605 PHILOSOPHICAL TRANSACTIONS. [aNNO i6Q2-3. 



1. I took a large bolt-head, holding about 3^ lb. of water, with a narrow 

 neck, to show the increase more sensible ; and having filled it with water, I 

 noted exactly to what mark the water rose ; then I immersed it into a skillet of 

 warm water, and let it stand so long, till I concluded the warm water had com- 

 municated its temper to the water included in the bolt-head : and I found, 

 that though the water was warm, much beyond the degree of the summer's 

 iieat, and notwithstanding it was winter; yet that gentle heat had scarcely any 

 effect in dilating the water, so that it hardly appeared to have ascended in the 

 neck of the bolt-head. Then I took the skillet, and set it over the fire ; when 

 it was observable that the water, as it became hot, ascended slowly in the neck, 

 especially at first; but after it began to boil in the skillet, the expansion became 

 more visible, and it ascended apace, till such time as it stopped again, the ut- 

 most effort of boiling water being able to raise it no higher. Then, having 

 ^made a mark at the utmost height to which it had risen, I took it out, and had 

 the satisfaction to observe, that though it was not raised so high without a very 

 strong boiling, yet it subsided very slowly, as retaining some time the space it 

 had acquired from the heat, even after the heat was passed, and the glass was 

 8o cool as to be touched without burning the fingers. However, the next 

 morning I found it reduced to the first mark, where it stood when at first 

 put in, having lost nothing sensible by evaporation during the experiment, 

 which I attribute to the length of the neck wherein the vapours were condensed 

 into drops before they reached the top. I then examined how much water 

 would raise that in the neck, to the mark whereto it had been increased by 

 boiling, and found it was a 26th of the bulk of the first water, which on 

 repeated experiment I found to be true. But it was obvious that water, in- 

 creasing so very little with ^11 the degrees of heat the air receives from the 

 sun, was a very improper fluid to make a thermometer of; and besides, any 

 freezing liquor is useless for this purpose in these northern climates. 



2. I took a smaller bolt-head, with a proportional cane or neck, and filled it, 

 after the same manner, with mercury, and having boiled it as above, I observed 

 that 125 ounces of mercury had increased by the space of 810 grains, or a 

 74th part of its bulk when cold. But it was very remarkable, that whereas a 

 gentle heat had scarcely any effect on water, here on the contrary, the mercury 

 did sensibly ascend at first, and had almost attained its greatest expansion before 

 the water boiled in the skillet. And after it boiled, though I let it stand very 

 long over the fire, I could not discern that the most vehement boiling had any 

 effect on it, above what appeared when it first began to boil. The mercury 

 being taken out, it subsided as it cooled, and in a few hours returned to the 

 mark where it stood before it was put into the water. This fluid being so sen- 



