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Mr. Charles Tomlinson on [Dec. 20, 



shape and grow into fine octahedral forms, increasing from the bottom 

 upwards, with the usual evolution of heat. 



Two similar flasks in my study, containing sodium sulphate, were 

 pricked with a pin ; one crystallized immediately and the other did not. 

 Next day I enlarged the opening into the second flask to the size of a 

 small pea, and after two or three hours the solution became solid. 



Pellogio and others claim for sponge and other absorbent bodies a 

 nuclear action. I immersed three bits of sponge in boiling water, and 

 took them out with forceps and put them in a dinner-plate, which together 

 with the forceps were placed in the kitchen oven. Three flasks, contain- 

 ing sodium sulphate solution (3 salt to 1 water), prepared the day before, 

 were taken into the kitchen, and the bits of sponge, now dry, hard, and 

 warm, were taken up with the forceps and dropped severally into the flasks, 

 which were covered with small beakers. The flasks were put upon the 

 window-ledge in my study. One of the solutions crystallized after eight 

 hours ; the other two formed a good deal of the modified salt, in which 

 the sponge became entangled : the second solution crystallized on the 

 third day ; the third solution had not crystallized after ten days, although 

 it was repeatedly shaken ; the beaker was then taken off, and the solution 

 crystallized within half an hour. In all three cases the sponge soon 

 absorbed a portion of the solution and became thoroughly soaked ; the 

 solutions were exposed to considerable cold in the window, the weather 

 being chilly, but the sponge was quite inactive. 



Such results as these are certainly in opposition to the absorption 

 theory ; but the difficulty in this, as in other parts of the subject, lies in 

 the fact that one observer, in an apparently carefully conducted experi- 

 ment, finds sponge, charcoal, and other porous bodies to be nuclear, while 

 another equally good observer (M. Viollette, for example) declares them 

 to be inactive. In trying the effect of vapours on these solutions some 

 years ago, a sponge dipped in ether, chloroform, bisulphide of carbon, &c. 

 was held over the surface : whenever the sponge touched the surface 

 crystallization set in ; or passing the sponge hastily over the surface the 

 portion adhering to the sponge crystallized immediately, while the solu- 

 tion in the vessel did not. 



In repeating Prof. Grenf ell's experiments on drops, I find the same 

 spirit of contradiction to prevail. The solutions which with him are so 

 permanent are transitory with me. I found sodic sulphate solutions of 

 various strengths, from six parts of salt to one of water, to one part of 

 salt to one of water, to be sensitive in every room of my house and on 

 every kind of surface on which they were deposited. My method was to 

 boil the filtered solution in a clean flask and then to cover the neck with 

 a small beaker. A couple of dropping-tubes (constantly kept in water, 

 except when in actual use, so as to keep them free from nuclei) were 

 employed for getting a supply of the solution from the flasks. A large 

 drop, made up of 5 or 10 or more single drops, was in this way deposited 



