Chemistry: xix 
Vapour of sulphuric ether ......., 302°379° 
naphtha. ...... bso fe! 177-870 
oil of turpentine. ...... 177-870 
nitric acid (sp. gr. 1°494) 531-990 
ammonia (sp. gr. 0°978). 837:280 
vinegar (sp. gr. 1:007).. 875000 
The latent heats of the vapours of the last three liquids in this 
table are obviously composed of the latent heat of the acids, and 
the alkali supposed in a state of purity, and of the steam of the 
water with which these bodies are united in the liquids distilled. 
There is probably an error in the estimation of the latent heat of 
vinegar. The best vinegar that I eyer met with contained only 
about six per cent. of acetic acid. Now I can hardly believe 
that so small a quantity could lower the latent heat of steam 
almost a ninth part. This surely could scarcely happen even if 
we were to suppose that acetic acid in the state of vapour has no 
latent heat at ail. 
5. Laws of Cooling.—Newton was the first person who gave a 
theory of the cooling of bodies. He took it for granted that the 
quantity of heat lost by a body in given small times was propor- 
tional to that which the body retained (considering the heat of 
the body to be the excess of its temperature above that of 
surrounding air). Hence it followed that if the times of cooling 
were taken in arithmetical progression, the losses of heat ought 
to form a decreasing geometrical progression. ‘Trusting to the 
accuracy of this principle, he calculated the melting points of 
lead, tin, and various other bodies, by observing a red-hot piece 
of iron on which these metals were placed, and noting the times 
when they respectively became solid. When the iron became 
cold enough to admit the application of a thermometer, he 
applied that instrument, and measured the times of cooling, till 
the metal acquired the temperature of the surrounding air. He 
then calculated backwards to determine the initial temperature 
of the red hot iron, and the temperatures at which the respective 
metallic bodies attached to the iron lost their fluidity. 
In the year 1739, Dr. Martine, of St. Andrew’s, published a 
very ingenious paper on the heating and cooling of bodies, in 
which he showed, by a great number of experiments, made both 
by himself and by Muschenbroek, that the Newtonian law does 
not hold correctly ; that bodies cool more rapidly than that law 
supposes ; and that if it were rigidly accurate, hot bodies would 
take an infinite time to cool down to the temperature of the 
surrounding air. But a few years later, Kraft and Richman, 
endeavoured to demonstrate the truth of the Newtonian law by 
experiments. And notwithstanding the various evidences that. 
have been produced from time to time of the inaccurary of that 
law, it has continued to be admitted by chemists in general, 
and constituted the basis of the experimental investigations of 
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