Royal Society. 389 



combustible mixture consisted of six or seven parts oxygen to 

 one of fire-damp. With mixtures of atmospheric air it is also 

 combustible ; and il appears that even one part fire-damp to 

 SO parts of the atmosphere increased the flame of a candle, and 

 gave it a blueish tinge; but that with one part fire-damp to 15 

 parts atmospheric air it is perfectly harmless. It required two 

 parts oxvi^en to one of fire-damp to produce one jiart of car- 

 bonic acid. Lastly, one part of azote or of carbonic acid ren- 

 ders it -vvhoily incombustible; and as the chimney of vSir Hum- 

 phry's "Safe Lantern" must necessarily be always supplied with 

 this gaseous matter, it is scarcely possible to conceive any thing 

 more effectual, or more likely to answer all the expectations of 

 the most sanguine philanthropist. It seems, reasoning theore- 

 tically, to combine in an unprecedented degree all the requisites 

 cf simplicitv, portabili'tv, (Kconomy and efficacy, which are ne- 

 cessary to the common purpose of manual labour. We cannot 

 therefore doubt that it may be the means of preserving many 

 useful lives, and tliat it will prove to the coal-miners a " per- 

 fectly safe lantern." 



The reading of a paper by F. Daniel, Esq. F.R.S. wa& begun, 

 and continued on 



Nov. 23. It was An experimental Inquiry into the Process of 

 Crystallization, and the Effects of Solution on the Structure of 

 Crystals. The author's object was to verify, if possible, the hy- 

 pothesis of the sphericity of molecules. He began by making 

 solutions of alum, nitrates of copper and of potash, &:c. These 

 solutions took two or three weeks to yield regular crystals; 

 they began by depositing a sediment which gradually assumed oc- 

 tohedral, rhomboidal, &:c. forms. Experiments of this nature 

 he varied with great industry and ingenuity, and detailed n.i- 

 nutely the results. His next object was to observe the changes 

 which took place in crystals during solution. He weighed cer- 

 tain crystals, immersed them in a given portion of water, left them 

 to remain in the fluid so many hours, then withdrew them, wined 

 them dry with blotting pajjer, ascertained what weight they had 

 lost, and what were the modifications produced on their crystal- 

 line structure : he again immersed them in water for a limited 

 time, and repeated his observations. This process he continued 

 some davs, always carefully noting the changes evinced on the 

 exterior form of the crystals, the modulations or changes of their 

 angles, the operations of the solvent on their faces, sides or sum- 

 mits, the parts which disappeared entirely or became truncated, 

 &c. These results were illustrated by figures, without which it 

 would not have been possible to render them intelligible. A 

 considerable diversity occurred in the changes which the different; 

 crystals experienced j but all were more or less truncated, at 



B b 3 least 



