fome 'fhermometrical Experiments. 523 
that i° of heat, according to Fahrenheit’s thermometer, 
increafes the bulk of a quantity of quickfilver of T7 ^ 9 - 6 - w ths 
parts, viz. if the bulk of a quantity of quickfilver in the 
temperature of 50° is equal to 100,000 cubic inches, the bulk 
of the fame quantity of quickfilver in the temperature of 51 0 
will be equal to 100,009 cu bic inches. 
It is almoft fuperfluous to mention, that the cavity of the 
tubes employed for thefe experiments, muff be perfectly uni- 
form throughout. The fcales to be ufed for this method 
fhould be fo exadt as to be turned by the hundredth part of a 
grain when charged with about half an ounce weight. 
From thefe obfervations the method of graduating, or of 
determining the length of a degree in a new thermometer, is 
eafily deduced, the only requifites for the calculation being the 1 
weight of a quantity of quickfilver,, which fills a known 
length of the tube, and the weight of the whole quantity of 
quickfilver contained in the thermometer when filledi Sup- 
pofe, for instance, that in making a new thermometer it 
be found, that the weight of fo much quickfilver as fills five 
inches length of the tube is equal to ten grains, and that the 
weight of the whole quantity of quickfilver contained in the 
thermometer weighs 300 grains. It is plain, that if the 
whole quantity of quickfilver weighs 300 grs.- parts 
of it muff weigh 0,027 S r * But Bie weight of fo much mer- 
cury as fills five inches of the tube is equal to 10 grains; 
therefore, 0,027 gr. weight of quickfilver muff fill 0,0133 
inch of the tube, and this is equal to the length of i °, or the 
double, treble, &c. of it is equal to two, three, See. degrees. 
By this >• means the fcale may be made; that is,, it may be 
divided into degrees,, but the numbers cannot be added to them 
without finding which, of thofe degrees, correfponds with the 
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