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brilliant objects when viewed by polarised light. Metals 
reduced in this manner require re-grinding several times 
before they lose their fibrous character, and become suffi- 
ciently minute for successful experiments. 
Metallic oxides vary considerably in their form and 
magnitude, according to the solutions from which they are 
precipitated. By practice it would be possible in many 
cases, by their microscopical appearance, to name the solu- 
tions from which they had been precipitated. The activity 
of these, when of favourable size, say from the s-o&ooth to 
Toovoth of an inch, is very different, being great in water, 
solution of gum, sugar, &c., but quite inactive in oil. 
Mercury and sulphur when sublimed assume a spherical 
form, and although these spheres could be obtained from 
ToVoth to 5 o o o oth of an inch in diameter, they do not exhibit 
any movement in water. He has sublimed them on to a 
drop of water, but they refused to sink. Possibly their 
polished surfaces retained a film of air which floated them. 
So transparent and perfect in form are the sulphur spheres that 
they distinctly exhibited the image of a lamp flame at their 
focal point. Triturated or precipitated sulphur will exhibit 
active movement in various solutions. As regards the cause 
of this so-called molecular movement, Mr. Dancer thinks that 
chemical action will not account for it. Diamond dust, 
graphite, and other refractory substances, are found to be 
active in water and solutions of gum. Nor is electricity a 
satisfactory explanation to him. He has found that parti- 
cles did not show a marked alteration in their movements, 
when exposed to electrical influence. The results of many 
experiments point to heat as a probable cause, and although 
