SPECIFIC
, in Philosophy, that which is proper and peculiar to any thing; or that characterises it, and distinguishes it from every other thing. Thus, the attracting of iron is Specific to the loadstone, or is a Specific property of it.
A just definition should contain the Specific notion of the thing defined, or that which specifies and distinguishes it from every thing else.
Specific Gravily, in Hydrostatics, is the relative proportion of the weight of bodies of the same bulk. See Specific Gravity.
Specific Gravity of living men. Mr. John Robertson, late librarian to the Royal Society, in order to determine the Specific gravity of men, prepared a cistern 78 inches long, 30 inches wide, 30 inches deep; and having procured 10 men for his purpose, the height of each was taken and his weight; and afterwards they plunged successively into the cistern. A ruler or scale, graduated to inches and decimal parts, was fixed to one end of the cistern, and the height of the water shown by it was noted before each man went in, and to what height it rose when he immersed himself under its surface. The following table contains the several results of his experiments:
| No. | Height. | Weight. | Water | Solidity. | Wt. of | Specific |
| of | raised. | water. | gravity. | |||
| men. | Ft. In. | lbs. | Inches. | Feet. | lbs. | (Wat. 1) |
| 1 | 6 2 | 161 | 1.90 | 2.573 | 160.8 | 1.001 |
| 2 | 5 10 3/8 | 147 | 1.91 | 2.586 | 161.6 | 0.901 |
| 3 | 5 9 1/2 | 156 | 1.85 | 2.505 | 156.6 | 0.991 |
| 4 | 5 6 3/4 | 140 | 2.04 | 2.763 | 172.6 | 0.801 |
| 5 | 5 5 7/8 | 158 | 2.08 | 2.817 | 176.0 | 0.900 |
| 6 | 5 5 1/2 | 158 | 2.17 | 2.939 | 183.7 | 0.849 |
| 7 | 5 4 3/8 | 140 | 2.01 | 2.722 | 170.1 | 0.823 |
| 8 | 5 4 1/8 | 121 | 1.79 | 2.424 | 151.5 | 0.800 |
| 9 | 5 3 1/4 | 146 | 1.73 | 2.343 | 146.4 | 0.997 |
| 10 | 5 3 1/8 | 132 | 1.85 | 2.505 | 156.6 | 0.843 |
| medium | 5 6 2/3 | 146 | 1.933 | 2.618 | 163.6 | 0.891 |
| of all. |
One of the reasons, Mr. Robertson says, that induced him to make these experiments, was a desire of knowing what quantity of timber would be sufficient to keep a man afloat in water, thinking that most men were specifically heavier than river or common fresh water; but the contrary appears from the trials above recited; for, except the first, every man was lighter than an equal bulk of fresh water, and much more so than that of seawater. So that, if persons who fall into water had presence of mind enough to avoid the fright usual on such occasions, many might be preserved from drowning; and a piece of wood not larger than an oar, would buoy a man partly above water as long as he had strength or spirits to keep his hold. Philos. Trans. vol. 50, art. 5.
From the last line of the table appears the medium of all the circumstances of height, weight, &c; particu- larly the mean Specific Gravity, 0.891, which is about 1/9 less than common water.
