OCCASIONAL NOTES.

THE ROOSEN METHOD OF PRESERVING FISH.

We have already noticed the method recommended by Professor Cossar Ewart of preserving fresh fish with boracic acid and salt. Mr Roosen of Hamburg has patented another method, which was lately tested in Edinburgh. The process consists in the salmon being placed in an air-tight compartment among a solution of boracic acid, salt, and water, and a heavy pressure being applied, the solution penetrates and thoroughly disinfects the fish, which are prevented from decaying, and retain all their strength and nourishment. On the 15th of February, a steel barrel, made for the purpose, and capable of holding about three hundred pounds of fish, was filled with salt water containing about fifty per cent. of boracic acid, and into this compound five splendid salmon, fresh from the Tay, were placed. The air having been entirely withdrawn, the barrel was hermetically sealed, a pressure of six atmospheres, or ninety pounds to the square inch, being applied. After standing for seventeen days, the barrel was opened on the 4th of March, and all the salmon were found in as fresh and healthy a condition as when they were first placed among the solution. The flesh of the fish was of a beautiful colour, and could not be distinguished from that of a fresh salmon placed alongside of it, while the blood began to flow freely immediately on the salmon being cut up. The salmon was served up at a luncheon, on the following day, in different forms of cooking, and the general opinion was that the new method of preservation was upon the whole successful. The fish was of good flavour and colour; it could be separated in nice flakes, and the curd was well preserved.

A NEW BOILER-FEEDER.

The problem of feeding boilers has yet to be solved, no method yet introduced having by its intrinsic merits superseded all others. At the present time, injectors or donkey-engines are usually employed—the former being an ingenious apparatus which forces the feed-water into the boiler by the rush of steam through a narrow orifice; the latter differing in no way from an ordinary pumping-engine, and usually deriving its power from the boiler itself. Both these systems of feeding require constant supervision; and it is to obviate the necessity of continued attention and the risk resulting from carelessness, that boiler-feeders automatic in action have been designed. So far, their application has not been extensive; but a recent improved design, patented as ‘Mayhew’s Automatic Boiler-feeder,’ bids fair to push its way even in these times of depressed trade, when boiler-owners not unnaturally hesitate to incur any outlay, however slight, which a rearrangement of the boiler-feed necessarily entails. The apparatus consists essentially of two vessels—the upper of copper, the lower of cast-iron. An ingenious valve-arrangement connects the former with the boiler, whilst the latter is connected with the supply of feed-water. When the water in the boiler falls below a certain level, the end of the pipe connected with the upper vessel becomes uncovered, and the steam being free to enter it, operates on the valves, thereby admitting a charge of water to the boiler from the copper vessel. A vacuum is formed in the copper vessel, which now recharges itself from the one beneath, ready for another operation. As many as five charges a minute can thus be obtained. Should the apparatus, from any cause, fail to work, and the water fall too low, a fusible plug melts and sounds an alarm whistle. It is satisfactory to note that an ingenious straining arrangement works well for feeding with dirty water—the great difficulty in all apparatus of this class, owing to the valves becoming choked. The feeder may be regarded as safely beyond the mere experimental stage, a large number already being in operation in different works throughout the country, and with results satisfactory in every respect.

SHOT-FIRING IN COAL-MINES.

A correspondent thus writes: ‘In your article on “Shot-firing in Coal-mines” you speak of the dangerous operation of tamping or plugging the shot-hole with brick or coal dust rammed hard. It must indeed be a dangerous operation; but cannot the hole be as effectually plugged without any danger at all? It is usual, after charging a rocket, to drive in dry clay upon the top of the fuse, to prevent its blowing through; but a layer of wet plaster of Paris poured in and allowed to set, dries harder than the clay, and obviates all danger from concussion or grit. Cannot the shot-hole be in like manner plugged? Plaster of Paris (gypsum or sulphate of lime) expands, not shrinks, when combined with water, so that it fills accurately every part of the bore. If the hole were slightly conical, the smaller end outwards, or made with an internal flange, the plaster would offer more resistance than the clay.’