440 Spheroidal Condition of Liquids at Common Temperatures. 



(3) The glass rod, with the drop hanging from it, may be lowered 

 upon the film several times so as to flatten the drop, without its 

 being absorbed. In some cases, however, there is contact between 

 the spheroid and the surface beneath at a single point ; for in 

 rolling about, the spheroid will sometimes leave a trail of liquid, 

 and so diminish in size until it suddenly vanishes by being ab- 

 sorbed. In all cases the drop vanishes suddenly, apparently by 

 flattening at its under surface, and thus coming into contact 

 with the liquid film below ; but at the moment of disappearing 

 a small globule is sometimes shot up from below, and this con- 

 tinues on the surface for a short time. 



The spheroid, whether rolling about or stationary, displays by 

 the rapid motions of its particles the struggle that is going on 

 between gravity and cohesion. If a minute portion of lycopo- 

 dium powder be shaken over the globule, and this rude treat- 

 ment does not cause it to break up, the powder will be seen 

 streaming rapidly down the outer surface of the spheroid, and 

 ascending by the central vertical axis to separate again at the 

 top, and stream over the surface again to the bottom — present- 

 ing, in fact, a figure something like that given in the books to 

 represent the boiling of water. 



The longer duration of a spheroid of the fresh or superior 

 over that of the common oil has been verified in a number of 

 cases. For example, a common oil of bergamot had a duration 

 of about 5", while that sold to me as a very choice oil (marked 

 super) lasted from 21" to 27". Rosemary lasted 7"; the distil- 

 late 13"; origanum 4" to 5"; the distillate 10" to 11". Several 

 paraffine oils from different makers showed great variations in 

 their cohesive force. 



There is one curious circumstance that must be noted, and that 

 is that a drop of one liquid will not form a spheroid on a film of 

 another liquid at ordinary temperatures ; or it does so with diffi- 

 culty, and the duration is very short. This remark applies to 

 the paraffine oils of different makers, and even to oils from 

 plants of the same genus. Thus the oil of Eucalyptus amygda- 

 lina will not assume the spheroidal condition on a film of E. oleosa, 

 or on one of E. goniocalyx. A drop of origanum is immediately 

 absorbed on a film of rosemary ; as is lavender or turpentine on 

 origanum ; but after these failures, a drop of the same kind of 

 liquid as that of the film will form a spheroid without much dif- 

 ficulty, other circumstances being favourable. 



In no case was I able by my method of experimenting to pro- 

 duce a spheroid of a fatty oil on a film of fatty oil at common 

 temperatures. No sooner, however, was heat introduced, than 

 the difficulty ceased. A very clear limpid sample of a fish-oil 

 was raised to 320°, and spheres, not spheroids, of fish and 



