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° c, 

 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 indefinitely 

 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 paraffin 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. 



