DEFINITIONS OF UNITS. (FROM SMITHSONIAN TABLES.) ACTIVITY. Power of rate of doing work ; unit, the Watt. " AMPFRE. Unit, of electrical current. The international ampere “which is one-tenth of the unit of current of the C. G. S. system of electromagnetic units, and which is represented sufficiently well for practical use by the unvarying current which, when passed through a solution of nitrate of silver in water, and in accordance with accompanying specifications, deposits silver at the rate of ooo1 I 18oo of a gram per second.” The ampere = I coulomb per second = 1 volt ạcross I ohm = Io" i E. M. U. = 3 x 1oo E. S. U. ( E M. U. = C. G. S. electromagnetic units. E. S. U = C. G. S. electrostatic units). Amperes = velts/ohms = watts/volts. Amperes x volts = amperes* x ohms = watts ANGSTORM. Unit of wave-length = 10" heter, ATMOSPHERE. Unit of pressure. English normal = 14.7 pounds per sq. in - 29-929 in. = 76oʻ 18 mm. Hg. 32° F. French normal = 760 mm of Hg. O’C = 29.922 in. = I47o lbs. per sq. in. BAR. A pressure of one dyne per cmo. BRITISH THERMAL UNIT. Heat required to raise one pound of water at its temperature of maximum density, I F. = 252 gram-calories. е че CALORIE. Small calorie =gram-calorie = therm = quantity of heat required to raise one gram of water at its maximum density, one degree Centigrade.
