RovAL Society 49 
more evident from experiments made in the months of i February 
and March, ( when the weather was realbnably cold, and not 
freezing) with water, mercury, and ipu-it of winej wherein the 
following particulars were very remarkable, i. Mi\ Halley took 
a large bolt-head, holding about 3 f //^. of water, with a narrow 
neck, to make the increafe thereof more fenfiblej and having 
filled it with water, he noted exa6lly to what mark the water 
role 5 then he immerled it into a ikillet of warm water, and let ic 
Hand fo long, till he concluded the warm water had communicated 
its temper to the water included in the bolt-head 5 and he found, 
that tho' the water was warm, much beyond the degree of the 
fummer's heat, and nctwithftanding it was winter, yet that gentle 
heat had fcarcely any effe6t in dilating the water, ib that it 
appeared to have alcended in the neck of the bolt-head ; then he 
took the fkillet, and fet it over the fire ; when it was obiervable, 
that the water, as it grew hot, did flowly afcend in the neck, 
efpecially at firft^ but after it began to boil in the fl-illet, the 
expanfio'n thereof became more vifiblc, and it alcended a-pace, till 
fuch time as it flopped again, the utmoft effort of boiling water 
being able to raife it no higher 5 then having made a mark at the 
greateft height, he took it out, and he obferved, that tho' it was 
not raifed fo high without a very ftrong boiling, yet it fubfided 
very flowly, as retaining for fome time the fpace it had acquired 
from the heat, even after that heat was over, and the glafs io cool, 
as to be touched without burning the fingers 5 however, next 
morning he found it reduced to the firfl mark, where it flood 
when at firfl put in, having lofl nothing vifibly by evaporation, 
during the experiment, which might be owing to the length of the 
neck, wherein the vapours were condenfed into drop.^;, before they 
reached the top 5 then he examined how much water would raife 
that in the neck, to the mark to which it had been di^aSed by 
boiling, and he found it was a 2 5th part of the bulk of the firfl 
watery which, upon repeated experiments, he obferv'd to be true 5 
but it was obvious, that water dilating fo very little, with ajl 
the degrees of heat the air receives from the lun, was a very im- 
proper fluid to make a thermometer withal^ and befides, any 
freezing liquor is ufelefs for this purpole in thele northern cli- 
mates. 2. He took a fmaller bolt-head, with a proportionable 
tube or neck, and filled it after the fame manner with mercury, 
and having boiled it as above, he obferved, that 125 ounces of 
mercury had occupied as much fpace as 810 grains, or a 74th part 
of its bulk when cold 5 but it was very remarkable, that whereas a 
gentle heat had Icarce any effect on water, here on the contrary, 
Vol. Ill G ths; 
