CHEMICAL SCIENCE. 209 



mysterious abodes, on a still larger scale and with an overwhelming 

 force. These substances will open up a new field for inquiry and 

 investigation for observation and experiments. They will play an 

 important part in all future geological hypotheses, when we have to 

 argue from the known to the unknown. They will fill many a gap in 

 imperfect observations, they will explain various phenomena, explode 

 rash assertions and imaginary assumptions. We may also hope, too, 

 for further information on the question, whether the fundamental 

 rocks of our planet, the form of which presumes a fluid state, were 

 soluble in water ; or whether the temperature of the earth was once 

 so high, that the ingredients of certain rocks were in a melted state ?" 

 He concluded by mentioning that, " amongst the products of smelting 

 furnaces there are some which have not yet been found in a natural state 

 Some of the artificial productions, however, have been subsequently 

 discovered in the realms of nature, and there is no reason why we 

 may not expect, with future investigations, to find the others." 



NEW TEST FOR MERCURY. 



MR. ARTHUR MORGAN in a paper read before the Dublin Medico- 

 chirurgical Society says, if a strong solution of iodide of potassium 

 be added to a minute portion of any of the salts of mercury, placed 

 on a clean bright plate of copper, the mercury is immediately depos- 

 ited in a metallic state, appearing as a silvery stain on the copper, 

 which cannot be mistaken, as no other metal is deposited by the same 

 means. By this method corrosive sublimate may be detected in a 

 drop of solution unaffected either by caustic potash, or iodide of 

 potassium. In a mixture of calomel and sugar in the proportion of one 

 grain to two hundred, a distinct metallic stain will be obtained with 

 one grain of the mixture, which of course contains 1-200 of a grain 

 of calomel ; in like manner, 1-400 of a grain of peroxide of mercury- 

 may be detected, although the mixture with sugar is not in the least 

 colored by it, with preparations of mercury in the undiluted state, this 

 process acts with remarkable accuracy, the smallest quantity of 

 calomel in peroxide of mercury, such as would almost require a mag- 

 nifying lens to perceive, placed on copper and treated with iodide of 

 potassium, wiU give a distinct metallic stain. 



The advantages of this test may be briefly stated as follows : It is 

 a delicate test inferior only to chloride of zinc and the galvanic test of 

 zinc and gold. It is easy of application. It requires a very small 

 portion of the substance to be examined a matter of no small impor- 

 tance. Acting on the insoluble as well as the soluble salts, it obviates 

 the intermediate process of solution. When it acts, its indications are 

 decisive. As to its disadvantages, the only one which seems tenable 

 is, that although it acts on minute portions, still that must be in a con- 

 centrated condition. 



