•228 MR. J. T. CUNNINGHAM ON 



some effect in determining the rhythm of these successive Aoavs, 

 but when the wax falls from a slightly greater height the effect 

 of the vibrations is seen in a series of large knobs on the lower 

 surface of the paraffin mass. 



Although, as remarked above, Kappers does not describe in his 

 paper how the shell-like masses were formed, he gives some 

 information on this question in a private letter to Mr. Burne, 

 which that gentleman has kindly sent to me. In this letter 

 Kappers states that since he obtained the specimens by accident 

 he has from time to time tried to make them purposely, but 

 always failed. They were formed by molten wax that escaped 

 between the embedding mould and the zinc table on which it 

 rested, the molten wax " coming soon in contact with water 

 (aqueduct water)." I presume that aqueduct water means what 

 we call tap-water. He goes on to say that it must be possible to 

 make the shapes purposely, that he tried to do this in watch- 

 glasses floating on water, and got some " which showed the 

 principle very clearly but were not nearly as nice as those 

 obtained by accident." The paraffin he used was a mixture of 

 2 parts melting at 58° C. and 1 part melting at 42° C. That 

 which I used melted at 52° 0. 



From these remarks of Herr Kappers it seems to me quite 

 certain that the specimens he obtained were formed in the same 

 way as mine, namely from molten wax flowing on to the surface 

 of water. He gives a sketch showing the embedding mould 

 resting on the metal table, but I presume from his remark about 

 water that the edge of the zinc table overhung a vessel of water, 

 such as a sink, and that the escaping wax flowed from the edge 

 of the table on to the surface of the water. It is certain that 

 no shell-like forms are produced by the wax cooling on a solid 

 surface ; I have tried this, and the only result is a plate of wax 

 of fairly uniform thickness of rounded outline and no special 

 markings either on the upper or lower surface. 



I have also tried the effect of pouring the wax into watch- 

 glasses floated in water, and found that concentric lines are 

 produced on the surface in contact with the glass. The lines in 

 this case are more circular round a centre in the middle of the 

 watch-glass, but they are not so distinct and regular as when the 

 wax is poured on to water. Their explanation is I believe the 

 same as in the latter case. 



Although I think it is quite evident from the facts and ex- 

 periments above discussed that the form and markings of the 

 shell-like masses have nothing at all to do with crystallization or 

 the forms of crystals, I have made some investigation of the 

 crystalline structure of the solidified wax, and give here the results 

 of this investigation. The crystals of the wax can be seen in thin 

 sections cut from a block, and have the form of elongated prisms. 

 A simple way of obtaining these crystals is to melt a little of the 

 wax on a microscope-slide and allow it to cool of its own accord, 

 iind then examine it with the microscope. The prisms are then 



