272, Progress in Science. [April, 
the next day the earth was covered with a layer having a mean thickness 
of between 7 and 8 centimetres. The temperature of the air rapidly fell on 
the gth, the minimum observed at the Jardin des Plantes was 20°7° C., and at 
the Observatoire 21°5° C. The table of observations of the temperatures 
observed at different depths beneath the snow-covered soil, show, however, 
that at no time was it lower than the zero of the centigrade scale in the case 
of the turfed ground, at depths of 0°05 m. and 0:03 m. At the depth of o'05 m., 
the temperature, starting about o’05° C., rose to 0°7° C.; at o-1 m. and 073 m. 
the temperatures were 1 and 2 degrees, and the variations 1 and ,%,ths of a 
degree, indicating a tolerably constant temperature at each station. At these 
depths, therefore, in ground of this kind, roots, seeds, and other organic 
bodies are preserved from the ill effects of a frost even of 20° below zero. In 
the case of denuded soil, it was otherwise from the 2nd of December to the 
6th, at a depth of 005 m.; the temperature was always below zero, and on the 
15th at zero. On the 7th it was 1°, after which it continued to fall till the roth, 
from which it again rosea few tenths daily up to the 15th. From the preceding 
observations, it therefore appears, that a bed of snow 7 or 8 centimetres 
in thickness, completely protects objects at a depth of 0:05 m. from even such 
a severe frost as 20° C., if the earth is turfed ; whilst when it is bare, the tem- 
perature at the same depth is 1°5° below zero. Seeds and roots will therefore 
be kept with perfe@ security in turfed ground, which, if the ground had been 
ploughed or otherwise tilled, would undoubtedly have perished. 
MM. Leygue and Champion have invented an apparatus for measuring the 
temperature of the detonation of explosive compounds. The apparatus 
is founded on the known distribution of the temperature in a metallic bar 
heated at one of its extremities, and consists simply of a copper bar of 0025 m. 
diameter and of 0-60 m. length. Small cavities are drilled in the bar at 
distances o‘ro m., these cavities being filled with oil in which the bulbs of 
small thermometers are immersed. The following are some of the tempera- 
tures of the detonation of the chief explosive compounds; the degrees are 
centigrade. Chassepot powder, 191°; fulminating mercury, 200°; Abel’s prot- 
oxide, 205°; sporting powder, 288°; picrate of potash, 336°; nitro-glycerine, 
256° to 257°; artillery powder, 380°. 
M. Fosselli has succeeded in producing an amount of cold just below 
the zero of the Fahrenheit scale by simple mechanical action, creating rapid 
evaporation. He employs a wheel formed of a spiral tube, both ends of 
which are open, set vertically and half immersed in the fluid to be cooled, so 
that the latter passes constantly through the whole length of the tube, half 
of which is constantly above the liquid, and being wet, gives rise to active 
evaporation and consequent refrigeration within it. 
M. Ch. Tellier describes an arrangement and apparatus whereby the 
vapourisation of ether is employed for the production of intense cold, provision 
being made to recover the ether in a very ingenious way, by causing it to be 
absorbed by sulphovinic acid, from which it is afterwards again separated by a 
simple distillation. An apparatus is now being made according to the 
author’s instructions with which it will be possible to manufacture a ton 
of solid ice per hour, while the apparatus, of great simplicity and without any 
complicated fittings, will admit of constant action, and thereby making the ice 
at a very low price. 
Mr. Fletcher has brought out an improved gas furnace and hot-blast blow- 
pipe. The speciality of this furnace is the burner. It is as simple as an 
ordinary Bunsen’s burner, but the flame is solid to the centre. Copper 
will fuse in any part of the flame; and to make a crucible furnace simply 
requires a support for the crucible, and a fire-clay jacket to prevent radiation. 
The lower part is a chamber 6 in. by 3 in., open at the bottom, in which the 
gas is partially mixed with air. This mixture is conducted to the top of 
the burner through a mass of fine tubes, with an arrangement to supply 
between each exactly the amount of air necessary to consume it instantly. A 
flame produced by this means, consuming 20 feet of gas per hour, is about 2 
inches high and almost colourless. The whole of the available heat is 
