764: Transactions of the Society. 



erosions of various kinds. In the first place there are a number of 

 scattered erosions of circular form varying in size from fine points 

 as seen under a 1/4 in. objective up to cavities three or four times 

 the diameter of a blood-corpuscle. Secondly, the surface of the 

 glass is marked by a number of lines taking various directions, 

 which must correspond either to original scratches on the surface 

 of the glass, or to lines of detachment of the paraffin. Erosion has 

 occurred along these lines in a beaded fashion, the size of the beads 

 corresponding with the size of the spherules of carbonate of lime 

 deposited. Thirdly, over considerable arese the entire surface of the 

 glass has gone. The floor of these depressed areae is marked with 

 closely approximated circular and dumbbell-shaped depressions, in 

 many of which an inner circle or concentric circles may be seen. 

 At first sight these inner circles appeared to indicate projections in 

 the centre of depressions ; but so far as I can make out by careful 

 focusing they are, in fact, deeper excavations marking a deeper 

 extension of the process of molecular disintegration of the glass. 



It is hardly necessary to point out that the last experiment — 

 with glycerin and carbonate of potash — was made in order to 

 determine the possibility of a solution of glass by carbonate of 

 potash, the occurrence of which would have introduced a difierent 

 element of a chemical kind. 



This, having evoked no response, enables us, I think, fairly to 

 fall back on Mr. Eainey's explanation of the phenomena occurring 

 in his own observations. I have mentioned that in addition to 

 glass slides I have used slips of mother-of-pearl and of ivory. 

 Here the paraffin kept the firm hold which I had hoped it would 

 maintain on the glass surface ; and I am able to show slips of this 

 kind in which, after removal of the paraffin, the word ANT is 

 clearly seen etched on the surface. The etching here occurred in 

 all the experiments, even in that where glycerin was used with the 

 carbonate of potash, a point of some interest when viewed in 

 certain aspects of these experiments. 



I wish to draw the following inferences from the experiments I 

 have related. First, that without the use of the acids or the 

 alkalies which are known to be capable of dissolving glass, a glass 

 surface may be eroded almost to opacity when placed in contact 

 with carbonate of lime and a colloid. Secondly, that the erosion so 

 efi'ected may be explained on the basis of Mr. Eainey's observations 

 on molecular coalescence. Thirdly, that, in contact with glycerin 

 and carbonate of potash, ivory and mother-of-pearl may be eroded, 

 although as far as can be seen, no spherules of carbonate of lime 

 are deposited. The first part of these conclusions is applicable to 

 Dr. Bidie's observations ; the third part has a difierent, and, as I 

 think, a wider application. 



Mr. Eainey's chapter on what he called " Molecular Disintegra- 



