27. 



as could be required. Wlien the cells were cut out, by placing them between 

 two ordinary glass slides, and applying a slight pressure, they could be 

 made as flat as possibly could be. He might also add, that although those 

 which he had described were square, yet rings might easily be cut out by using 

 two punches of different sizes. 



Dr. Matthews suggested that another method of flattening would be by rolling 

 the lead out upon a sheet of stout plate glass with a piece of glass barometer 

 tube, and he thought that by cross rolling the lead would be flattened better 

 than by simply rubbing it with a ruler. 



The Chairman observed that Dr. Bowerbank had used nothing else than 

 common tea lead for his smaller cells for many years past, and for larger cells 

 he used common plumbers' sheet lead. All his large collection of sponges were 

 mounted in this way. It did not, perhaps, have a very neat appearance, b*t 

 certainly answered the purpose very well. He believed that the doctor flattens 

 out the lead on a board. 



Mr. Smith said the cells were very easily made, so that two or three dozens 

 of them could be made in the course of half an hour. 



Mr. Richards said that some time ago he had to mount some wood sections, 

 and procured for the purpose some rather light tin foil, which he cut out into 

 cells with two punches, putting apiece of tube between them to keep them the 

 right distance apart. A solution of glue and treacle was used for fixing them j 

 this was laid on and allowed to dry first, and was found very useful in sticking 

 on the thin glass covers, as it only needed a slight moisture to render it 

 adhesive, whereas any liquid would have run under it and into so shallow a cell 

 as the one he had described. 



The Chairman remarked that this was carried out in a more perfect manner 

 in the cells introduced by Mr. Sufi'olk. 



Dr. Matthews said he found a difficulty in using these cells, because he could 

 not fix them on with marine glue, which required a temperature so high to melt 

 it that the tin cells were in danger of melting also. 



The Chairman remarked that he used nothing else himself but marine glue to 

 fix the tin cells to the slides, and it answered admirably. 



Mr. Smith said his method was to fix them by running a ring of gold size 

 upon the slide. 



The Secretary said he was very much obliged to Mr. Smith for bringing this sub- 

 ject before the meeting. For many years he had been in the habit of using cells 

 made of a thin kind of lead known as "pattern lead, ' which was used by 

 dentists for taking patterns for their gold plates. It would be found to answer 

 the purpose very well, and had none of the objectionable qualities mentioned 

 by Dr. Matthews, since the slide might be made almost red-hot without melting 

 the cells, and the cells were very easily stuck on with marine glue. For shallow 

 cells a simple ring of gold size, and gum dammar put on thickly and allowed to 

 get hard, answered the purpose very well, and if Bastian's cement were used 

 instead, the cell could easily be built up higher by adding layers upon those 

 which had become dry. Another way was to use the zinc cells, which would 

 stand any amount of heat; acid, however, would aff'ect these, but vulcanite cells 

 would resist acids. In making cells for mounting in fluid, it would be found of 

 great advantage to set up some standard size, and keep to it, as this would 

 enable the worker in a short time to estimate correctly the exact amount of fluid 

 required for filling — a matter of very much importance. 



Mr. Leifchild asked if Mr. White considered the vulcanite cells to be the best ? 



