28 Joty—On the Conservation of Mass. 
The method adopted finally for bringing the reacting substances together will 
best be understood from the figure, Plate V., which is approximately to natural 
scale. The vessels a and 0 are of lightest blown glass fused together. The upper 
holds the liquid substance; the lower the solid. The capacity of @ is about 
30 ¢.cs., of 6 about 50 c.es.; the solid is introduced into the lower vessel by means 
of the lateral tubule. The liquid is drawn into a by temporarily inserting a cork 
in this tubule perforated by a fine-drawn glass tube to which a rubber drainage- 
tube is affixed, and sucking on this while the tubule x is inserted in the measured 
quantity of fluid. This may be effected after the solid constituent has been 
inserted into d. The fine-drawn glass tube shown in the figure is then affixed 
between the tubule and x, the vessel being held approximately horizontal during 
the operation. This fine tube is not open throughout its length, but is stopped 
at the bend g by a very short plug of low melting-point substance. There is 
no difficulty in slipping the one extremity into the rubber cap fitted on x, and the 
cork into the tubule. The operation is easily effected without spilling a drop of 
the liquid. Placed finally in the upright position shown in the figure, it is evident 
that the melting of the plug at g will allow the liquid in a to gravitate gently into 
b, the air displaced from a circulating through the tube. To ensure that no air 
escapes or is sucked in, it is necessary to seal up the cork fitting the tubule 
with wax, and to varnish the rubber connexion at x with the same or other air- 
tight substance. The filled vessels are next placed in an outer paper cylinder, 
and very fine dry cork-dust (prepared by filing down cork of good quality) 
poured in around them. ‘The cylinder is freely suspended by fine copper wire 
from the extremity of the beam. 
The liberation of the liquid carried in the upper bulb is effected by radiation 
from a short ribbon of platinum (through which a current may be passed) over 
which the bend of the tube q¢ oscillates in its vibrations about the zero position of 
the beam. This platinum radiator is contained in a separate compartment to the 
front of the case enclosing the beam. The fine glass tube enters this cell through 
a slit between glass plates, and may be observed through an external window, 
so that the break-down of the plug may be assured. he necessity of the cell 
is obvious: disturbance of the air within the body of the case appears to be 
completely avoided or delayed by its use to such an extent that even trials 
of the radiator for periods much longer than those required to melt the plug 
produced no discoverable effect. The time actually required to melt the plug 
varies from one to three seconds, the platinum being raised to a visible red. 
The low melting-point substance consisted of a mixture of vaseline and parafin 
melting at 27°5° C. It might appear as if much difficulty would be experienced 
in getting the plug into the correct position in the flattened bend of the long, 
fine tube. But this is not so. In fact, a very little of the vaseline mixture 
