299 
Figure 1 represents a section, and figure 2 a front view of 
an apparatus. The same letters indicate the like parts; a a a 
aaa represent a series of thin vessels, by preference of cop- 
per, tinned, in the form of very short cylinders having the 
ends slightly raised or dished. These vessels are independent 
of each other, being connected by socket joints and pins, 
are suspended from a frame, and have a weight attached 
through the medium of pulleys. Each of the vessels contains 
a portion of sulphuric aether, and after the aether has been 
boiled therein so as to expel the atmospheric air, the aperture 
is sealed with solder ; such sealing is easily effected, if two 
apertures be made in any part of the apparatus, one about 
of an inch in diameter, and the other about T J S of an 
inch, and the larger one first soldered, the soldering being 
effected just when the aether has ceased to boil. In such 
apparatus the boxes are about eight inches diameter, and six 
in number, so that twelve flexible surfaces are combined ; the 
thickness of the copper is such that a square foot 
weighs about one pound. The weight may be varied from 
about five to fifty pounds, according to the temperature which 
the apparatus is intended to regulate. The proportions of 
the eccentric pulleys used are such, that when the weight is 
raised the tension upon the series of vessels is a little increased 
by leverage ; but when the weight has descended so as to 
turn the pulley about half round, on account of the varying 
leverage, the tension on the series of vessels becomes about 
five times that amount, but this will require adjustment by 
trial with each apparatus. When properly adjusted, the weights 
should have equal tension on the vessels throughout the half 
turn of the pulleys, as in the fusee of a watch; and the 
eccentrics are made with slots, so that they may be adjusted 
on the axis. 
Mr. Ward has found sulphuric aether the most 
suitable for temperatures ranging from 40° to 90° of 
