t 439 3 
Appendix to the foregoing Report. In a Letter from Mr. 
George Gilpin, Clk. R. S. to Charles Blagden, M. D. 
Sec. R. S. 
SIR, 
Having completed two instruments for trying the expansion 
of fluids, according to the method described by Mr. Ramsden, 
with a stopper going into a tube on the side of the ball, I now 
present you with an account of the experiments which I have 
made with them, that you may judge how far such instruments 
are deserving of notice. The scale of the longest admits of 
,26 of an inch for each degree of the thermometer, and that of 
the shortest ,17 of an inch for each degree. 
They were charged with pure spirit : some of the same that 
was made use of in our experiments by weight, specific gra- 
vity ,82514 : and having hung them up by the side of each 
other to a piece of wood, provided for the purpose, with the 
same sensible thermometer hanging between them that was 
used in our experiments by weight, I immersed them in a 
large quantity of water brought to the temperature of 6 o°, 
the one quite, the other nearly, to the height of the fluid in 
the stem. In this water they were suffered to continue until 
they had arrived at that temperature, when it was observed 
that the spirit in the tube of the long instrument stood at o, 
or the commencement of the scale, and the spirit in the tube 
of the short instrument stood at -ff o o o above o, which I shall 
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