USEFUL PROJECTS. 
mixture of pounded ice and water, ment with lampblack, and with very 
the times of cooling were observed pure and very dry wood-ashes: the 
as mentioned in the following table. results of which experiments were 
AO7 
I afterwards repeated the experi- 
The Bulb of the Thermometer surrounded by 
| 
176 grains of 176 grains 
fine powder of | fine powde 
charceal, 
Heat lost, 
79" 
gi” 
95 91 
100 109 
139 136 
196 192 
331 321 
_ 940 937 
charcoal. 
Exp. No. 24. Exp. No.25. 
as under mentioned: 
of 
rot 
307 grains of 
pure dry wood 
ashes, 
195 grains of 
lampblack. | 
| 
| 
| 
Exp. No. 26. | Exp No, 27. 
124" 
96" 
118 92 
164 107 
164 136 
257 185 
394 Sik 
1171 | 097 
The experiment, No. 25, was 
simply a repetition of that number- 
ed 24, and was made immediately 
after it; but, in moving the ther- 
mometer about in the former ex- 
iment, the powder of charcoal 
which filled the globe was shaken 
a little together ; and to this cir- 
cumstance | attribute the difference 
in ‘the results of the two experi- 
ments. 
In the experiments with lamp- 
black and with wood-ashes, the times 
taken up in cooling from 70° to 
60° were greater than those em- 
ployed in cooling from 60° to 50°. 
This most probably arose from the 
considerable quantity of heat cor- 
tained by these substances, which 
was first to be disposed of before 
they could receive and communicate 
to the surrounding medium that 
WG» i 
which was contained by the bulb of 
the thermometer. 
The next experiment I made was 
with semen lycopodii, commonly 
called witch-meal: a substance 
which possesses very extraordinary 
properties. It is almost impossible 
to wet it; a quantity of it strewed 
upon the surface of a bason of water, 
not only swims upon the water 
without being wet, but it prevents 
other bodies from being wet which 
are plunged into the water through 
it; so that a piece of money, or other 
solid body, may be taken from the 
bottom of the bason by the naked 
hand without wetting the hands 
which is one of the tricks common- 
ly shown by the jugglers in the 
country. This meal covers the hand, 
and, descending along with it to the 
bottom of the bason, defendsit from 
Cec4 the 
