Note 155 — Chapter III

Dr. Williams made some observations on this subject in 1789, and in 1791, but they generally belonged to the warmer months, and I do not know that any extensive series of comparisons between the temperature of the ground in the woods and the fields has been attempted in America. Dr. Williams's thermometer was sunk to the depth of ten inches, and gave the following results:

Time.Temperature of ground in pasture.Temperature of ground in woods.Difference.

May 23 52 46 6

" 28 57 48 9

June 15 64 51 13

" 27 62 51 11

July 16 62 51 11

" 30 65½ 55½ 10

Aug. 15 68 58 10

" 31 59½ 55 4½

Sept. 15 59½ 55 4½

Oct. 1 59½ 55 4½

" 15 49 49 0

Nov. 1 43 43 0

" 16 43½ 43½ 0

On the 14th of January, 1791, in a winter remarkable for its extreme severity, he found the ground, on a plain open field where the snow had been blown away, frozen to the depth of three feet and five inches; in the woods where the snow was three feet deep, and where the soil had frozen to the depth of six inches before the snow fell, the thermometer, at six inches below the surface of the ground, stood at 39°. In consequence of the covering of the snow, therefore, the previously frozen ground had been thawed and raised to seven degrees above the freezing point.—Williams's Vermont, i, p. 74.

Bodies of fresh water, so large as not to be sensibly affected by local influences of narrow reach or short duration, would afford climatic indications well worthy of special observation. Lake Champlain, which forms the boundary between the States of New York and Vermont, presents very favorable conditions for this purpose. This lake, which drains a basin of about 6,000 square miles, covers an area, excluding its islands, of about 500 square miles. It extends from lat. 43° 30' to 45° 20', in very nearly a meridian line, has a mean width of four and a half miles, with an extreme breadth, excluding bays almost land-locked, of thirteen miles. Its mean depth is not well known. It is, however, 400 feet deep in some places, and from 100 to 200 in many, and has few shoals or flats. The climate is of such severity that it rarely fails to freeze completely over, and to be safely crossed upon the ice, with heavy teams, for several weeks every winter. Thompson (Vermont, p. 14, and Appendix, p. 9) gives the following table of the times of the complete closing and opening of the ice, opposite Burlington, about the centre of the lake, and where it is ten miles wide.

Year.Closing.Opening.Days closed.Year.Closing.Opening.Days closed.

1816 February 9 1836 January 27 April 21 85

1817 January 29 April 16 78 1837 January 15 April 26 101

1818 February 2 April 15 72 1838 February 2 April 13 70

1819 March 4 April 17 44 1839 January 25 April 6 71

1820 { February 3 February } 4 1840 January 25 February 20 26

March 8 March 12 1841 February 18 April 19 61

1821 January 15 April 21 95 1842 not closed

1822 January 24 March 30 75 1843 February 16 April 22 65

1823 February 7 April 5 57 1844 January 25 April 11 77

1824 January 22 February 11 20 1845 February 3 March 26 51

1825 February 9 1846 February 10 March 26 44

1826 February 1 March 24 51 1847 February 15 April 23 68

1827 January 21 March 31 68 1848 February 13 February 26 13

1828 not closed 1849 February 7 March 23 44

1829 January 31 April 1850 not closed

1832 February 6 April 17 70 1851 February 1 March 12 89

1833 February 2 April 6 63 1852 January 18 April 10 92

1834 February 13 February 20 7

1835 { January 10 January 23 18

February 7 April 12 64

In 1847, although, at the point indicated, the ice broke up on the 23d of April, it remained frozen much later at the North, and steamers were not able to traverse the whole length of the lake until May 6th.