..^50.^ ^^^ .^ ^^ femperaium. ^ ^^ ^^ lii' 



tlkert pladi equal to 1^5^ mdre, o/'tpl 76^ below zero, 

 which I can hardly suppose, though the mercurial thermo- 

 meter used in these experiments fell lower than 270^* 

 below zero. If my former statement be erroneous^ it cer-' 

 tainly is not attributable to the mode of calculation, as ap- 

 prehended by M. Tardy de la Brossy. As it does not appear 

 that he had made any experiment on the subject, he could 

 not have anticipated this inaccuracy in the weight of silver: 

 and as he says that only a few grains of the increased gra- 

 vity of the mercury was attributable to the alcohol, he could 

 not be aware of the great increase of the specific gravity of 

 alcohol shown at I, by the same mode of calculation used' 

 in my essay, the subject of his animadversions. "-'"^ 



It is still, however, obvious, that mercury would not be 

 of the specific gravity which I attributed to it, unless it had 

 followed the same rate of contraction after it became solid a^ 

 it did whilst fluid : tiie evidence of the increased loss of weight'' 

 is so much against me, that I cannot defend that experi- 

 ment; and I would now be understood to carry my observa- 

 tions on the specific gravity of mercery, with accuracy, t'or 

 tbe point of congelation only; or to slate that near 56^ be- 

 low zero its specific gravity is 14*465, as by calculation at L, 

 Then, if we attribute to mercury in a solid state nearly' 

 double the contraction of silver as at H, or '00100 in each 

 degree, as it is near to its point of fluidity, we shall arrive 

 only at the specific gravity 14*483, as is shown at M. 



To ascertain whether the silver at C, with which I pro- 

 posed to compare the mercury, had expanded or contracted 

 by the deprivation of heat to which it had been exposed, 



H — I took an ingot of silver, \6 inches long, 2 inches 

 wide, and half an inch thick, weighing nearly 100 ounces; 

 and provided an instrument for the purpose of measuring 

 accurately the contraction and expansion of the silver, 

 by fixing in a piece of well baked wood two centre pins, 

 exactly 15 inches from each other, one of them very find, 

 for the purpose of striking an arch of a. circle on the surface 

 of the silver, when the other was fixeld in a perforation made 

 in the silver by the centre itself. Then, on the surface of the 

 bar of silver, heated to a pale red, an arch was described with 



V^ol, 30. No. U8. March 1808. K this 



