FACTS AND OBSERVATIONS. 
357 
every place on the globe has two different mean temperatures, 
one independent of terrestrial radiation, the other entirely 
dependent upon it. The latter M. Becquerel calls ‘‘ cli- 
materic,^^ because it serves to characterise the climate with 
regard to temperature. The former, which is obtained by 
placing thermometers at a certain height above the ground, 
varies with the latitude; the other is obtained by taking the 
average of observations made at different points of the place 
experimented on. In England, where the quantity of rain 
is about the same in each season, the difference between the 
two temperatures is zero. In Germany and Sweden, where 
there is more rain in summer than in winter, springs have a 
higher temperature than the average of the place; in Norway 
and Italy, where winters are rainy, the temperature of springs 
is lower. 
Formation of Hippuric Acid. —The production of 
IIi]}punc acid, the presence of which characterises the urine 
of the Herbivora, is due to the large quantity of carbon con¬ 
tained in their food. It, however, like urea, is not formed 
directly from the food, but is a result of the metamorphosis 
of the nitrogenous tissues. 
Its existence in urine is proved by evaporating it to one 
third of its bulk, and then adding hydrochloric acid. In a few 
hours linear and branch crystals will appear. 
Test for Bile-acids. —The editor of the Chemical News 
says, that the simplest way to test for bile-acids in urine is 
to put about a couple of drachms of the urine into a test-tube, 
drop in a fragment of white sugar of the size of a pea, and 
then add slowly, by pouring down the side of the tube, a 
drachm of strong sulphuric acid. If bile-acids be present, 
a fine violet or purple colour will be produced at the line of 
contact of the urine and the acid ; if absent, only a browning 
of the sugar will be observed. ' 
Uses of Petroleum. —Mr. Holmes states that the crude 
oil preserves wood for all time; the Indians bathe in it to 
heal wounds ; that it may be burnt in locomotives to generate 
steam, cotton waste being placed on the furnace bars, and 
the oil dropped on it by proper contrivances; it is the 
cheapest known agent for the production of light; that with 
care the process of rectification is perfectly safe; one of its 
products—benzine—is a substitute for oil of turpentine, and 
the heaviest oil is an excellent lubricator. 
XXXVI. 
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