664 “Co!, roy’s Experiments for 
difference. With the view of afcertaining this point, I 
procured four glafs rods near three feet long each, and of 
different diameters, the largeft being of the lize of the 
little finger, and the fmalleft about the thicknefs of a 
quill. One end of each, was fomewhat larger than the 
other, and was made perfectly fmooth, as that on which 
they were to reft when feverally meafured with the deal 
rod. They were then all placed in the tin veflel, in fuch 
a manner, as to admit pounded ice rammed very clofe 
around them, and the interftices to be filled with water. 
Having remained in that ftate a full half hour, they were 
feverally meafured with the deal rod, whofe length of 
3 2j inches was fcratched on each with the fharp edge of 
the file. This being done, the ice thrown out, and the 
veffel carefully wafhed, all the rods were replaced in it, 
immerfed in water, which afterwards was brought to boil. 
The fire being kept up, and the ebullition rendered as vio- 
lent as poffible for half an hour, the glafs rods were then 
feverally meafured, by applying them one after another 
to the deal rod, Handing with them in the boiling water. 
The experiment was repeated three times, on as many dif- 
ferent days, without its being poffible to difcern, that any 
of the glafs rods had dilated more than that of deal, from 
a difference of temperature of 1 8o°. In all of them, the 
freezing mark feemed accurately to coincidewith the top 
of 
