290 APPENDIX. 



It is an axiom in hydrostatics, that every substance which 

 sivims on water, displaces so much of the water as is ex- 

 actly equal to its own weight ; whereas, when a substance 

 sinks in water, it displaces water equal to its bulk. Take 

 a piece of hard wood, balance it accurately in a pair of 

 scales with water, and then place it gently in a vessel on 

 the surface of water which will flow over the top of the ves- 

 sel. If the wood be now taken out with care, it will be 

 found that the water in the scale will exactly fill the va- 

 cancy left by the wood. — lb. 



The specific gravity of bodies is denoted in chemical 

 writings by comparing it with the specific gravity of pure 

 water, in decimal figures, water being always considered 

 as 1.000. Thus the. specific gravity of the strongest sul- 

 phuric acid (oil of vitriol) is 1.850, or nearly nine tenths 

 heavier than water. Iron is 7.650, or more than 7| times 

 heavier than water ; that is, a cubic inch of iron, if put 

 into a scale, would require 7| inches of water to balance 

 it ; silver is 10.470 ; gold 19.257 ; andplatina21.2500,or 

 21 times heavier than water. 



All substances that Jloat upon water are specifically 

 lighter than it, as oils, alcohol, &.c. There are various 

 instruments which, when dropped into liquids, indicate, 

 upon a graduated scale, their specific gravity, be it heavi- 

 er or lighter than water, as the areometer, hydrometer, 

 Sue. Thus the juice of the apple or grape is heavier than 

 water in proportion to the quantity of sugar which it con- 

 tains ; and after fermentation, it becomes specifically 

 lighter than water in the same ratio, the sugar, which 

 was heavier, being converted into alcohol, which is lighter 

 than water. The tendency of wine or cider to run into 

 the acetous or vinegar fermentation, is in proportion to its 

 lightness before, and heaviness after fermentation — the 

 lighter the must, the heavier the liquor, and the less sugar 

 in the former, and less alcohol in the latter. The specific 

 gravity of apple-juice varies from 1.000 to 1.091. Some 

 we lately tried, from mixed fruit, indicated 1.063 by Bau- 

 me's areometer. — Con. 



A pint measure of atmospheric air weighs nearly nine 

 grains ; whereas a pint measure of hydrogen gas weighs 

 little more than half a grain. The same measure of pure 

 water weighs upwards of one pound avoirdupois. 



It may be remarked, that the Creator has endowed at- 

 mospheric air with the property of preserving its own 



