90 Mr. R. J. Moss, 
force has to be exerted to keep it afloat, or in other words, the 
greater must be the disparity of the velocities of the molecules 
of the intervening medium; and to produce this disparity there 
must be a considerable difference of temperature between 
the spheroid and the liquid on which it floats. In the case of light 
liquids there is less force to be exerted, and therefore a slight 
difference of temperature suffices. I find melted paraffin supplies 
all the requirements of the case. It is light, its sp. gr. at 15° ¢, 
being 0°86, while in the liquid state it is much lighter. On 
placing ordinary paraffin in a shallow silver basin and melting it 
I found that drops in the spheroidal state were easily obtained 
at temperatures not greatly exceeding the melting point of the 
paraffin, They are very easily obtained at 80°-90° C, and by 
directing a current of cool air over the surface of the liquid 
they may be kept in existence for a considerable time. I have 
kept them afloat for more than twenty minutes without any 
special attention to the temperature of the paraffin or the strength 
of the current of air employed to keep the drops cool, and I have 
no doubt that with care their existence might be indetinitely 
prolonged. I have devised a method for performing the experi- 
ment in a closed flask in which any gas may be contained, and 
at any desired tension; my experiments with this apparatus are, 
however, not yet completed. 
For the purpose of ascertaining whether there was any appre- 
ciable evaporation from melted paraffin at a temperature favour- 
able to the existence of spheroids, I placed three porcelain cap- 
sules containing paraffin on an iron plate, and heated them until 
a thermometer placed in one of them rose to 90° C. One of the 
capsules was then allowed to cool, and weighed, after which it 
was replaced on the hot plate and kept there for two hours, 
during which time I occasionally produced spheroids on the 
paraffin in the third capsule, some of these lasting a considerable 
time. When the weighed capsule was allowed to cool and again 
weighed I found a very slight increase had taken place. On 
repeating the experiment twice similar results were obtained. I 
therefore decided upon performing the experiment in vacuo for 
which purpose 5°5 grammes of the paratin that had been re- 
peatedly heated in one of the capsules was transferred to a 
small flask which was attached to an air pump and exhausted. 
