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accidents especially. The composition of most patent foods, as 
Revalenta Arabica, principally of some form of starch. The 
adulteration of food — of butter by Thames mud, beef suet, &c. ; 
of milk by water, sheep's brains, chalk, &c. ; of tea, the com- 
position of Malo's mixture, Lie tea, its principal adulterations. 
The use of the microscope in the detection of them. Eread is 
frequently adulterated, chiefly with rice and potatoes to cause it to 
absorb more water as well as an intrinsic adulteration. Alum is 
found in most specimens, used to whiten the bread and cause it to 
absorb more water. 
ABSTRACT OF ME. PENGELLT's PAPER. 
(Read November 17tli, 1870.) 
The meteorology of the present year (1870) has been so remark- 
able as to be calculated to impress every one with the importance 
of the subject of Rain, and to give every thoughtful person a 
desire to know something of the machinery by which that essential 
of life is supplied to us. E-ain is largely due to the agency of 
Electricity and Heat, but on the present occasion it will be dealt 
with so far only as it is a thermal phenomenon. 
There have been various speculations respecting the nature of 
Heat, but at present it is regarded as a Mode of Motion — a motion 
of the molecules or atoms of bodies. Among its effects on matter 
the following are prominent: — Temperature^ Ex'pansion^ Liqiief ac- 
tion, and Vaporization. The heat which produces any one of these 
cannot at the same time do any other work, — cannot produce any 
one of the others : thus, ice and water at 32° Fahr. have the same 
temperature but not the same amount of heat, for the heat required 
to produce and sustain liquefaction is, were it now so employed, 
capable of raising the temperature of the same quantity of water 
from 32° to 172°, that is through 140° Pahr. In like manner, the 
heat required to convert water at 212° to steam at the same 
temperature is capable of raising the temperature of the same mass 
through 990° Eahr. Again, high pressure steam has a higher 
temperature than that given off by ordinary boiling water, but 
