Replies.

HARDMAN'S ACCOUNT OF WATERLOO.

(Vol. viii., p. 199.)

The book for which G. D. inquires is, A Descriptive Poem of the Battle of Waterloo, and Two previous Days, dedicated to the Earl of Carlisle, by Captain Hardman, London, 1827, 8vo., pp. 28. It appears from the dedication that he was adjutant to the 10th Royal Hussars, of which the Hon. F. Howard was major. He says:

"We breakfasted together in the hovel on the 18th, in the morning, as stated in the poem; and during that dreadful bloody day, he and I were frequently discoursing about our situation; the good position occupied by us; the humane feeling of our brave Duke for choosing that situation to save men's lives; and once during the day our regiment was completely sheltered; all the balls from the enemy flying over our heads, except one that dropped about six yards from the major and me. We were at that time dismounted about twenty minutes, to rest the horses. I took the ball up; we looked at it, and had a good hearty laugh over it."

Here is the description referred to:

"At three in the morning I went to Major Howard,—

The prose description of the charge is clear and vivid:

"When we advanced to decide the destiny of the day, our right squadron was in front, led on by the brave Major-General Sir. H. Vivian, commanding our brigade; Lord Robert Manners commanding our regiment; Major Howard commanding the right squadron; and I, the adjutant, in front with those officers. Just as we began to advance, I said, 'Major, what a grand sight we have before us!' 'Yes, it is,' said the major. These were the last words he spoke, for in half a minute afterwards we were right amongst them, slashing away; then there was no time to talk. We quickly made them turn their backs towards us; but there was one square of infantry that stood firm. That square made sad havoc among us. The major was killed by that square. He was not six yards from the muzzles of the French firelocks when he was shot. He fell off his horse, and, I believe, never moved a finger; but I had not a moment's time to stop, for we had not then cleared the field. This, my lord, is a true account of the last moments of your lordship's late son, and one of the best friends I ever had."—P. iv.

Then follow some reflections which I abstain from quoting, as the way in which they are expressed would produce an effect quite contrary to the author's intentions. The burial is thus described:

The criticism of the note quoted by G. D. is sound: "Hardman was no poet, but he could describe graphically what he saw and did." The poem seems to have been the result of a sudden thought. In the dedication he says it was not begun till May 18, and "A Letter to the Right Hon. George Canning," appended to it, is dated June 4. In the letter he says, that if he "can get into the printing-house again without loss," he will answer Mr. Canning effectually on the Catholic question. He also hopes "to get before the public every week," and "to show that all gentlemen professing the law are the most abused, and at the same time more honest than any other class in this kingdom." Had the last-mentioned hope been fulfilled, I think I should have heard of it. I have not met with any other work bearing Captain Hardman's name; and probably his printer's bill (he was his own publisher) put an end to his literary career.

I subjoin two specimens of the poem which, though not relating to the subject of G. D.'s Query, may be interesting if you have room for them, as such poetry is not published every day. An exhortation to good conduct ends thus:

The other describes his own narrow escape, and the death of an artilleryman:

H. B. C.

U. U. C.

DATES OF BIRTHS AND DEATHS OF THE PRETENDERS.

(Vol. viii., p. 565.)

Though it is much to be regretted that the dates in question are not recorded on the Stuart monument in St. Peter's, yet the deficiency is in part supplied by the cenotaph raised to the memory of his elder brother by Cardinal York, in his cathedral church at Frascati. From it we find that Charles Edward deceased on 31st January, 1788, at the age of sixty-seven years and one month. This date also fixes the year of his birth at 1720, and the month December; most probably the 28th, though often given as the 31st. We give a copy of the inscription below.

The date of the birth and decease of James III. is correctly given in "N. & Q.," Vol viii., p. 565.

An account of the sepulchral monument of the last of the Stuarts may interest the readers of "N. & Q." In the south aisle of St. Peter's, and against the first pier of the nave, is the monument of the Stuarts. It was sculptured by Canova to the memory of James, the old Pretender; Charles Edward, the young Pretender; and Henry Benedict, the Cardinal, who was known in Rome as Cardinal York. Part of the expense of the monument was defrayed by George IV., who sent a donation of fifty pounds for the purpose to Pius VII. The monument is built on to the masonry of the pier, of white marble, about fifteen feet high, and is in the form of the frustrum of a pyramid, and surmounted above the entablature by the royal arms of England. Below the arms are profile portraits in bas-relief of James, Charles Edward, and Henry Benedict, surmounted by a festoon of flowers. Beneath the portraits is the following inscription:

"Jacobo III. Jacobi II. Magnæ Brit. regis filio, Karolo Edvardo, Et Henrico, decano Patrum Cardinalium, Jacobi III. filiis, Regiæ Stirpis Stuardiæ postremis. A.D. MDCCCXIX. Beati mortui, Qui in Domino moriuntur."

There is a representation of panelled doors, as if leading to a vault, below the inscription, though their sepulchre is not in this locality; a small triangular slab of marble surmounts the door, with the words "Beati mortui," &c. A weeping angel in bas-relief guards the doorway on each side; the head of each angel resting on the bosom, the wings drooping, the hands elevated, joined together, and resting on the end of an extinguished and inverted torch. The figures of the two angels are exquisitely beautiful, and among Canova's finest works.

The bodies, however, of these last representatives of a fallen line are not buried beneath this monument, but in the crypt under the dome, and in that portion of it called the "Grotto Vecchie." There, in the first aisle to the left on entering, against the wall, a tomb about six feet long by three broad contains all that remains of the ashes of the last of the Stuarts. Over it is a plain slab of marble, with an inscription to announce that this is the burial-place of "James III., Charles III., and Henry IX., Kings of England." Even in death this royal race has not abandoned the claim they were unable to enforce.

Opposite to this monument is the monument of Maria Clementina, daughter of James Sobieski, and grand-daughter of John Sobieski, King of Poland, wife of James III., and mother of Charles Edward and Henry Benedict. She married on 3rd September, 1719, and died at Rome on 18th January, 1735. The monument stands against the wall over the door leading to the staircase by which the public ascend to the cupola. Pietro Bracci carved the monument from the design of Filippo Barigioni, consisting of a pyramid of porphyry on a base of Porta Santa marble, the whole relieved by a ground of blue sky and clouds painted on the wall. Under the elevated pyramid is the sarcophagus of porphyry, above which are two marble statues, one of Charity, and the other of an infant, which support a circular medallion portrait in mosaic, of Maria Clementina, by Cav. Cristofori, from a painting by Lewis Stern. Drapery of Sicilian alabaster, with a fringe of gilded bronze, falls in ample folds on both sides of the sarcophagus, which is flanked by two angels, one holding a crown and the other a sceptre; and upon it the words are carved "Maria Clementina M. Britann. Fr. et Hibern. Regina." It was erected by the "Fabbrica di S. Pietro," at the cost of 18,000 scudi. There is another monument in Rome to Maria Clementina, and it is in the church of the SS. Apostoli, in the nave, upon the second pier on the right-hand side. It contains her heart, and consists of a circular urn of verde antico, surmounted by a crown, over which two angels hover, of white marble; and below, a tablet of rosso antico, bearing an inscription, thus:

"Mariæ Clementinæ Magnæ Britanniæ Etc. Reginæ, Fratres Min. Cons. venerabundi pp. Hic Clementinæ remanent præcordia, nam cor Cælestis fecit ne superesset amor."

Charles Edward has also another monument in addition to the one in St. Peter's, namely, at Frascati, fourteen miles from Rome, of which see Cardinal York was bishop. Its position is to the left of the great entrance door; the inscription runs thus:

"Hic situs est Karolus Odoardus, cui pater Jacobus III., Rex Angliæ, Scotiæ, Franciæ, Hiberniæ, primus natorum, paterni juris et regiæ dignitatis successor et hæres, qui, domicilio sibi Romæ delecto, Comes Albanyensis dictus est. Vixit annos LXVII et mensem: decessit in pace pridie Kal. Febr. anno MDCCLXXXVIII.

"Henricus Card. Episc. Tusculan., cui paterna jura titulique cessere, Ducis Eboracensis appellatione resumpta, in ipso luctu amori et reverentiæ obsequutus, indicto in templum suum funere multis cum lacrimis præsens justa persolvit fratri augustissimo, honoremque sepulchri ampliorem destinavit."

Henry Benedict, or Cardinal York, was born at Rome on 6th of March, 1725. He was Bishop of Ostia and Velletri, Dean of the Sacred College, Vice-Chancellor of the Roman Church, Arch-priest of St. Peter's, and Prefect of the Fabric of St. Peter's. He deceased at Frascati in July, 1807. In the church at Frascati, on the left hand of the entrance into the sanctuary, there is a monument in his honour; but I have not a copy of the inscription.

It is needless to add that though all these monuments are made of the richest marbles, and at great cost, the effect produced by them as Christian sepulchral monuments is unsatisfactory in the extreme. The inscriptions upon them are in equally bad taste.

Ceyrep.

"COULD WE WITH INK," ETC.

(Vol. viii., p. 648., &c.)

I agree with your learned correspondent Mr. Margoliouth, that the authorship of the lines alluded to must be ascertained by comparing the whole, and not by a single expression. It seems to me highly probable that they were suggested, either by the Chaldee hymn quoted by your correspondent, or by the lines of Chaucer, quoted "N. & Q.," Vol. viii., p. 180. I cannot, however, agree that the popular lines in question are a are a translation of the Chaldee hymn. The improbability will appear, if we compare them (as given "N. & Q.," Vol. viii., p. 127.) with the following version of the hymn; which, although metrical, will be found sufficiently literal:

This hymn, I admit, is more succinct than the popular lines; but at the same time I cannot but think that its author was indebted to the passage in the Koran ("N. & Q.," Vol. viii., p. 422.), immediately, or through Chaucer; who has not only the general sentiment as there found, but also—

I am equally convinced, that Mahomet himself took the thought from the passage in the New Testament, as suggested by your correspondent E. G. R. Each successive writer appears to have added something to what he borrowed. But when the Evangelist, John, had said, "The world itself would not be able to contain the books that should be written," it was easy for one writer to suppose an inkstand capacious as the sea; and for another to supply parchment, pens, and scribes ad libitum. That the phrase in the Koran should now be common in the East, is not wonderful, considering the extent to which Mahomedanism has prevailed there. After all, I do not think that the additions are any very great improvements. Without disputing about tastes, I may say at least that, for my own part, I greatly prefer the simplicity of the original idea, as expressed by the beloved disciple.

J. W. Thomas.

Dewsbury.

MACKEY'S THEORY OF THE EARTH.

(Vol. viii., pp. 468. 565.; Vol. ix., p. 89.)

A friend called on me this morning with the Number containing a notice of S. A. Mackey, supposing that, being a neighbour, I could furnish a few particulars of that extraordinary man. The whole of his MSS. came into my possession after his demise. Amongst these was a MS. of his Life, written by himself, and of which I took a faithful copy: which I have transcribed for gentlemen who wish to possess a copy. I am ready to furnish any gentleman with a copy, neatly written, book included, for 5s. It consists of fifty-two pages large demy 4to. The original is in the possession of a Mr. Brereton of Flitcham, near Lynn, Norfolk, to whom I sold all the MSS., Mr. Brereton being an intimate friend of S. A. Mackey.

I have on sale a copy of Mr. Mackey's Works, selected by Mr. Shickle, another intimate friend; neatly done up in coloured cloth. Also a copy of his Mythological Astronomy, with copious notes, in one hundred pages. Also, an Appendix of forty-eight pages. And another copy of the MS. Astronomy, with notes; but minus the Appendix.

I may as well inform you, that a friend of mine has in his possession a half-length full-size portrait of Mr. Mackey; admirably executed, and in prime condition, in a handsome frame. I believe it is for sale. I assure you, when I first saw it, I felt at the moment a kind of impulse to shake hands with my old friend and neighbour.

I shall feel great pleasure in answering any inquiries, so far as my knowledge extends. His Life is truly interesting; being that of a man born in sorrow, and cradled in adversity. Like him, I am a self-taught humble individual, and in my eighty-second year.

J. Dawson.

15. Doughty's Hospital, Calvert Street, Norwich.

In July, 1830, Sampson Arnold Mackey delivered a course of six "astro-historical lectures" in a large room near the Philanthropic Institution. The attendance was full, considering the subject, and I was surprised at the admiration which many well-educated persons expressed for his strange theories, to which they seemed to give full assent. To me his calculations and etymologies appeared as good as those of Pluche, Sir W. Drummond, Volney, and Dupuis, but no better. I met him at the house of the late Dr. Wright, then resident physician to Bethlehem Hospital. He was quiet and unassuming; but so perfectly satisfied that he had proved his system, that though ready to explain, he declined to answer objections, or defend his opinions. As a remarkable example of "the pursuit of knowledge under difficulties," he excited sympathy, and I believe that he disposed of all the copies of his various works then unsold.

H. B. C.

U. U. Club.

DO CONJUNCTIONS JOIN PROPOSITIONS ONLY?

(Vol. viii., pp. 514. 629.)

As my name appears to have been referred to by two of your correspondents, Mr. Ingleby and H. C. K., in connexion with the above question, I request to be permitted to state my real views upon it, together with the grounds upon which they rest. In doing this I can only directly refer to the observations of H. C. K., not having seen those of Mr. Ingleby to which he makes allusion.

Admitting that there are many conjunctions which connect propositions only, I am unable to coincide with the view of my friend Dr. Latham and other grammarians, that the property is universal. And I agree with Mr. Ingleby, as quoted by H. C. K., in thinking that the incorrectness of that view may be proved. We possess the power of conceiving of any distinct classes of things, as "trees," "flowers," &c. And we possess the power of connecting such conceptions in thought, so as to form, for instance, the conception of that collection of things which consists of "trees and flowers" together. If we possess the power of performing this mental operation, we have clearly also the power of expressing it by a sign. This sign is the conjunction "and." It is assumed, what consciousness indeed makes evident, that the power of forming conceptions is antecedent to that of forming judgments expressed by propositions.

But even if we proceed to form a judgment, as "trees and flowers exist," it may still be shown that the conjunction "and" connects the substantives "trees," "flowers," and not propositions. For if we reduce the given proposition to the form, "trees exist and flowers exist," the conjunction becomes wholly superfluous. It adds nothing whatever to the meaning of the separate propositions, "trees exist," "flowers exist." Omit, however, the conjunction between the substantives in the original proposition, and the sense is wholly lost. What meaning can we attach, except by a convention, to the form of words "trees flowers exist." Now there is, I conceive, no more obvious principle in grammar than that the doctrine of the elements of speech should be founded upon the examination of instances in which they have a real meaning—in which their employment is essential, not accidental.

It is doubtless one of the consequences of the neglect of this principle, that the older grammarians have made it a part of the definition of a conjunction, that it is a word "devoid of signification" (φὼνη ἄσημος). See references in Harris, p. 240. Were the philosophy of grammar founded, as alone it truly can be, upon the laws of thought, I venture to think that such statements would no longer be accepted.

If the views which I have expressed needed confirmation, they would to my own mind derive it from the circumstance, that on applying to the original proposition that "mathematical analysis of logic" to which H. C. K. refers (not, I think, without a shade of scorn), it is resolved into the elementary propositions, "trees exist," "flowers exist," unconnected by any sign.

Let us take, as a second example, the proposition, "All trees are endogens or exogens." If the subject, "all trees," is to be retained, there is, I conceive, but one way in which the above proposition can mentally be formed. We form the conception of that collection of things which comprises endogens and exogens together, and we refer, by an act of judgment, "all trees" to that collection. And thus the subject "all trees," remaining unchanged, the conjunction "or" connects the terms of the predicate, as the conjunction "and" in the previous example connected those of the subject. I am prepared to show that this is the only view of the proposition consistent with its strictly logical use. If H. C. K. insist upon the resolution "any tree is an endogen, or it is an exogen," I would ask him to define the word "it." He cannot interpret it as "any tree," for the resolution would then be invalid. It must be applied to a particular tree, and then the proposition resolved is really a "singular" one, and not the proposition whose subject is "all trees."

Not only do conjunctions in certain cases couple words, but in so doing they manifest the dominion of mental laws and the operation of mental processes, which, though never yet recognised by grammarians and logicians, form an indispensable part of the only basis upon which logic as a science can rest. And however strange the assertion may appear, I do not hesitate to affirm that the science thus established is a mathematical one. I do not by this mean that its subject is the same as that of arithmetic or geometry. It is not the quantitative element to which the term is intended to refer. But I hold, with, I believe, an increasing school of mathematicians, that the processes of mathematics, as such, do not depend upon the nature of the subjects to which they are applied, but upon the nature of the laws to which those subjects, when they pass under the dominion of human thought, become obedient. Now the ultimate laws of the processes which are subsidiary to general reasoning, such as attention, conception, abstraction, as well as of those processes which are more immediately involved in inference, are such as to admit of perfect and connected development in a mathematical form alone. We may indeed, without any systematic investigation of those laws, collect together a system of rules and canons, and investigate their common principle. This the genius of Aristotle has done. But we cannot thus establish general methods. Above all, we cannot thus establish such methods as may really guide us where the unassisted intellect would be lost amid the complexity or subtlety of the combinations involved. How small, for instance, is the aid which we derive from the ordinary doctrines of the logicians in questions in which we have to consider the operation of mixed causes and in various departments of statistical and social inquiry, in which the intellectual difficulty is almost wholly a logical one.

For the ground upon which some of these statements are made, I must refer to my recently-published work on the Laws of Thought. I trust to your courtesy to insert these remarks, and apologise for the undesigned length to which they have extended.

G. Boole.

Queens College, Cork.

ROBERT BLOET.

(Vol. ix., p. 105.)

Robert, Earl of Moreton, and Odo, Bishop of Bayeux, the Conquerors uterine brothers, both accompanied William, acting conspicuous parts on his invasion of England in 1066. The former died about 1090. Odo had been elected Bishop as far back as 1049. In 1088 he headed a conspiracy against William II.; but being defeated at Rochester, retired to Normandy. The time of his death is uncertain, but is supposed to have occurred in 1096.

The first notice of Robert Bloet's name, is as a witness to one of the charters of William II. to the monastery of Durham, granted in 1088 or 1089. He was appointed Chancellor in 1090, consecrated Bishop of Lincoln in 1093, and died in 1123.

These dates plainly prove that he was not "identical" with Robert, Earl of Moreton; and scarcely could be called cotemporary with him.

His supposed relationship to Odo is affirmed by Richardson, in his notes to Goodwin de Præsulibus, from an expression in his grant of the manor of Charleton to the priory of Bermondsey (Claud. A. 8., f. 118., MSS. Hutton); in which he says, "quod pro salute animæ Dom. mei Willelmi Regis, et fratris mei Bajocens. Episcopi." If Odo be the Bishop here intended, the meaning of "fratris mei" may be translated, not in the natural, but in the episcopal sense, as brother of his order. But the grant is probably a forgery, or its date of 1093 incorrect, for at that time Odo was in exile; and Bloet would have scarcely ventured to insult the king, from whom he had just received rewards and advancement, by coupling with his the name of one who had been banished as a traitor.

For farther particulars, allow me to refer your correspondent Mr. Sansom to The Judges of England, vol. i. p. 103.

Edward Foss.

PHOTOGRAPHIC CORRESPONDENCE.

A Hint to the Photographic Society.—It has been objected to this Society, that beyond the establishment of its Journal, and the forming of an Exhibition, it has done very little to promote the improvement of the beautiful art it was specially intended to advance. Such objections are very easily urged; but those who make them should at least propose a remedy. It is in no unfriendly spirit that we allude to these complaints; and we well know how difficult it is for a body like the Photographic Society to take any important step which shall not be liable to misconstruction. We would however suggest, that among those endeavours which it would become the Society to make, there is one which might at once be taken, namely, to secure for the photographic public a good paper. The want of such an article is hourly felt. If the Photographic Society, following the example of the Society of Arts, should appoint a Committee to take this matter into consideration, to define clearly and unmistakeably the essentials of a good negative paper for calotypes (for perhaps it would be well to keep to a good negative paper), and offer a premium for its production, a very short time would elapse before specimens of such an article would be submitted for examination. It is clear that the premium need be one only of small pecuniary value; for the fact of a maker having produced such an article as should gain the prize, would secure him an ample recompense in the enormous demand which would instantly arise for a paper which should be stamped with the public approval of a body entitled to speak with so much authority on such a subject as the Council of the Photographic Society.

Test for Nitrate of Silver.—The Reader of Photographic Works, who in Vol. ix., p. 111., asked for information as to how he might know whether nitrate of silver was pure, can detect any impurities with which that salt is likely to be contaminated, by applying a few simple tests to an aqueous solution of it. The impurities which nitrate of silver most frequently contains are nitrate of copper, nitrate of potash, and free nitric acid. It is also sometimes intentionally adulterated with nitrate of lead. The presence of a salt of copper is detected by the solution assuming a blue colour when mixed with an excess of ammonia. To detect nitrate of potash, hydrochloric acid should be added to the solution in sufficient quantity to precipitate the whole of the silver. The liquid should then be freed from the precipitate by filtration, and evaporated; if nitrate of potash is present, a fixed residue will remain after evaporation. The presence of a salt of lead is detected by adding a few drops of sulphuric acid to the solution of nitrate of silver, which precipitates the lead as sulphate if present. It is, however, necessary to dilute the acid with a considerable quantity of water, and, if any precipitate forms, to allow it to subside previous to using it as a test for lead, as ordinary sulphuric acid is frequently contaminated with sulphate of lead, which is soluble in the strong, but not in dilute, acid.

Any free nitric acid in the nitrate of silver can be detected by the smell. The crystals can be freed from it, should they contain any, by fusing them in a porcelain crucible over a spirit-lamp. The ordinary fused lunar caustic of the surgeon is unfit for general use as a photographic agent.

J. Leachman.

Professor Hunt's Photographic Studies.—My attention has just been directed to a "Practical Photographic Query" in your Journal, Vol. ix., p. 41., which appears to require a reply from me. It is quite evident that your correspondent, notwithstanding the personal respect which he professes to entertain, cannot have any intimate knowledge of either my works or my studies. Allow me to make my position clear to him and other of your readers. My first photographic experiment dates from January 28, 1839, and since that period the investigation of the chemical phenomena of the solar rays has been the constant employment of all the leisure which a busy life has afforded me. The production of photographic pictures has never been the ultimate object at which I have aimed, although my researches have caused me to obtain thousands. My object has been, and is, to endeavour to obtain some light into the mysteries of the radiant force with which the photographic artist works, being quite content to leave the production of beautiful images to other manipulators.

As I write on the subject, it appears, of course, necessary that I should be familiar with all the details of manipulation in each process which I may describe. Whenever I have mentioned, in either of my works, a process with which I have not been entirely familiar, I have given the name of the authority upon whom I have depended. But there will not be found in either my Photography, or my Researches on Light (of which a greatly enlarged edition will soon be submitted to the public), any one process upon which I have not made such experiments as appeared to me necessary to my understanding the rationale of the chemical changes involved, and of the physical phenomena which arise.

Now, since it is not necessary to select a picturesque object to instruct me in these points, the same buildings, trees, and plaster casts have been copied times beyond number; and when the problem under examination has been solved, these pictures have been destroyed.

There are twenty exhibitors of pictures in the Photographic Gallery who would certainly leave my productions far behind, as it concerns their pictorial character; but I am confident there is not one who has made the philosophy of Photography so entirely his study as I have done.

I have been engaged for the last two years in studying the chemical action of the prismatic spectrum. I inclose you my report on this subject to the British Association for 1852 (that for 1853 is now in the hands of the printer), from which you will perceive that I am employing myself to greater advantage to photography, as science under art, than I should be did I enter the lists with those who catch the beauties of external nature on their sensitive tablets, and secure for themselves and others pictures drawn by the solar pencil, in which no one can more deeply delight than your humble servant.

Robert Hunt.

Waxed-paper Pictures.—Will your correspondents or yourself do me the favour to say, how such beautiful pictures have been produced and exhibited by Mr. Fenton and others by the waxed-paper medium, if that process be so bad and defective? When I have followed it, and exercised consistent patience, I have ever produced pleasing and faithful results. That when parties do not themselves prepare, it becomes expensive, I am willing to admit; but I am inclined to attribute many failures to the uncertain heat of hot irons, which must vary; and I make this fact known to you as the result of my own observation on many sheets: added to which, defective manipulation, or impure chemicals, must not be allowed to do away with its having much merit.

Harley Lane.

The Double Iodide Solution.—In a note appended to Dr. Mansell's communication on the calotype (Vol. ix., p. 134.), you state that having lately prepared the double iodide solution according to the formula given by Dr. Diamond, in which it required 650 grains of iodide of potassium to dissolve a 60-grain precipitate, you were inclined to believe, until you made the experiment yourself, that Dr. Mansell must have made a wrong calculation as to the quantity of iodide of potassium (680 grains) which he stated was sufficient to dissolve a 100-grain precipitate, as the difference appeared so small for a solution more than one-third stronger.

The small difference referred to with respect to the quantity of iodide of potassium required, is owing to the amount of water used being in both cases the same. A slight difference in the strength of a solution of iodide of potassium makes a great difference with respect to the quantity of iodide of silver it is capable of dissolving. Thus, if you remove a small proportion of the water from a solution of the double iodide of silver by evaporation, the slight increase of strength which the solution will thereby acquire, will enable it to take up a much larger proportion of iodide of silver than it already contains; and if, on the other hand, you dilute it with a small proportion of water, its diminished strength (unless the solution contains a great excess of iodide of potassium) will cause the precipitation of a large proportion of the iodide of silver. And hence the great variation in the amount of iodide of potassium which is found requisite to form a solution of the double iodide of silver, under the same apparent conditions with regard to the proportions of the other ingredients employed, may be accounted for by the impossibility of measuring off with sufficient accuracy the proper proportion of water.

Whenever exact quantities of liquids are required, recourse should always be had to the balance, for no great accuracy can be depended upon by measurement with our ordinary glass measures, even supposing them to be correctly graduated, which is not always the case.

J. Leachman.

Dr. Mansell's Process.—Dr. Mansell's lucid and very practical paper on the calotype process in "N. & Q." must, I am sure, be of the greatest service to photographers in general; and as one of the many I am irresistibly tempted to offer my sincere and hearty thanks to him for the truly valuable hints it contains. If Dr. Mansell will give the rationale of the necessity of not allowing a longer time than absolutely required for the soaking out the now injurious iodide of potassium, set free by the deposit of the iodide of silver; and also, an explanation of the cause of that part of the iodized papers which takes the longest time in drying being weaker than that part which had been more hastily dried, the learned Doctor will still be adding to our present account of obligation to him.

Henry Hele.