IN THE HALL OF THE ROYAL SOCIETY. 
545 
fall of this quantity in the tube occasioned a rise in the level of that in the 
cistern of one inch and a half, affording a correction of very nearly 004 inch 
for ten inches. Everything having been thus prepared for the final experi¬ 
ment, a fire was lighted under the boiler at 11 a.m. of the 13th of June, and at 
half-past one pure steam issued with force from the cock (s) on the top of the 
boiler. When this was closed, the water began to rise slowly and steadily in 
the tube, oscillating at times about one inch and a half. More than an hour 
elapsed before the column of liquid reached the thermometer (c, d) at the 
upper end, when its temperature was found to vary from 85° to 90°. It still 
continued to rise very gently, till it issued with some force in an unbroken 
jet from the small tube which had been adjusted to the stop-cock. Three 
pints of water were thus drawn off, and the thermometer rose to 110°. The 
stop-cock on the top of the tube was then closed, and the cock on the top of 
the boiler simultaneously opened. The steam rushed forth from the latter with 
great violence, and after a considerable interval the column began very gently 
to fall from the top, without any boiling, or the slightest indication of air-bub¬ 
bles. When it appeared to be stationary, the sealing was attempted; the 
small part of the tube, to which the stop-cock was attached, was successfully 
drawn off and closed without the slightest disturbance of the column of water; 
but in cooling it unfortunately cracked. The fissure thus occasioned was very 
minute, but rendered the resumption of the whole process necessary. The 
most difficult part of this to effect, was the drawing off and contraction of the 
tube to fit it again for sealing. It was determined, upon consideration, not to 
replace the stop-cock, but to rely upon the pressure of the operator’s thumb to 
cut off the communication with the external air during the sealing. 
As it was necessary to the operation that the tube should be turned upon its 
axis, it was unpacked from the stuffing-box of the boiler, and loosened from its 
different supports; and everything was again successfully adjusted with great 
dexterity by Mr. Newman, who overcame the difficulties of these various pro¬ 
cesses with the greatest skill. It would be tedious to repeat the further steps 
of the progress; the boiling was conducted precisely in the manner which I 
have just described, and the tube was finally and permanently closed on the 
18th of June. Not the slightest speck or air-bubble has from that moment 
been detected in the column of water. 
