Mr. E. Solly's Description of an Electric Thermometer. 391 



being wholly changed into carbonic oxide, nitrogen, and me- 

 tallic oxide during a protracted subjection to the red heat of 

 iron in a porcelain crucible, after having made a great many 

 trials in vain. 



Paracyanogen is like carbon, boron, and silicon, in present- 

 ing two distinct forms, the unignited and the ignited; with all 

 the intermediate conditions. In the former state it gives nitro- 

 gen away at the incipient red heat of iron, though slowly and 

 without force enough to overcome any considerable pressure ; 

 while in the latter it requires at least the white heat. On this 

 account ignited paracyanogen may be mistaken for ignited car- 

 bon, and an operation said to have failed, which would have 

 succeeded if it had been finished. Paracyanogen is in every 

 way a tantalizing thing to make experiments upon. 



My white heat for copper is the temperature at which the 

 metal is white to my eye, and yet solid; when it is swelled 

 out to the utmost verge of solidity, and is about to fall down 

 liquid. This, too, needs management. As to the fusion of 

 sulphate of lime, it is needless to speak of every contingency. 

 To know the accidental from the essential is the problem of 

 scientific authorship. 



In fine, the alleged conversion of carbon into silicon is be- 

 fore the world, at least unencumbered by presumptuous ex- 

 planations, and not disgraced by anything like a challenge. 

 If others fail to procure the same results, I shall be sorry; but 

 so long as my observations continue to lead me on to others 

 of a more and more practical kind, I shall be very well content 

 to have my first publication regarded as a plenary mistake, 

 and will refrain from writing any more till it shall have be- 

 come impossible not to succeed in the performance of my 

 operations. I have, Sir, the honour to be, 



• Your obedient Servant, 



3 Dartmouth Row, Blackheath, Samuel MorisoN BROWN, 



near London. 



LIX. Description of an Electric Thermometer. By E. Solly, 



Jun., Esq. 



To Richard Taj/lor, Esq. 

 My dear Sir, 



I AM induced to send you the following account of a little 

 thermo-electric arrangement, believing that it may be in- 

 teresting to some of your readers ; for although there is little 

 or no novelty in the principles on which its action depends, 

 I am not aware that it has been before practically employed. 

 I had for some time experienced considerable inconvenience 



