Life of Sir Humphry Davy. 359 



lecture, which we regret we have not space to copy. In the lecture, 

 Davy observes, that * an historical detail of the progress of the inves- 

 tigation, of all the difficulties that occurred, of the manner in which 

 they were overcome, and of all the manipulations employed, would 

 far exceed his limits/ upon which Dr. Paris observes that, * to the 

 chemist, every circumstance connected with a subject of commanding 

 importance is pregnant with interest;' and having, by permission of 

 the managers of the Royal Institution, obtained leave to examine and 

 make extracts from the Laboratory Register, he obtained the following 

 interesting clue to ' the intellectual operations by which his mind 

 ultimately arrived at the grand conclusion.' With these interesting 

 MS. volumes we hope to make the reader acquainted in a future 

 page of this Journal in the meantime we shall follow Dr. Paris : 



4 It appears from this register, that Davy commenced his inquiries into 

 the composition of potash on the 16th, and obtained his great result on 

 the 19th of October, 1807. His first experiments, however, evidently did 

 not suggest the truth ; he does not appear to have suspected the nature 

 of the alkaline base until his last experiment, when the truth flashed 

 upon him in the full blaze of discovery. His first note, dated the loth, 

 leads us to infer that he acted on a solid piece of potash, under the sur- 

 face of alcohol, and several other liquids in which the alkali was not 

 soluble ; and that he obtained gaseous matter which he called at the mo- 

 ment " alkaligen gas," and which he appears to have examined most 

 closely, without arriving at any conclusion as to its nature. On the fol- 

 lowing day, he, for the first time, would seem to have developed potassium 

 by electric action on potash, under oil of turpentine, for the note records 

 the fact of " the globules giving out gas by water, which gas burnt in 

 contact with air ;" and then follows a query " Does if (the matter of 

 the globules) " not form gaseous compounds with ether, alcohol, and the 

 oils?" Here then he evidently imagined, that the matter of the globules, 

 which he had never obtained from potash, except when acted upon under 

 oil of turpentine, had formed gaseous compounds with the ether, alcohol, 

 and oils, in his previous experiments, and given origin to that which he 

 had termed " alkaligen gas" He then leaves the consideration of this 

 gas, and attacks the unknown globules, which probably did not present 

 any metallic appearance under the circumstances he saw them, for they 

 must have been as minute as grains of sand. I rather think that he com- 

 menced his examination by introducing a globule of mercury, and uniting 

 it with a globule of the unknown substance, for his note says " Action 

 of the substance on mercury, forms with it a solid amalgam, which soon 

 loses its alkaligen in the air/' And from the note which succeeds, he 

 evidently considered this alkaligen (potassium) volatile, as he says, " it 

 soon flies off on exposure to the air." 



' October 19. It is probable that, in consequence of the property which 

 the unknown substance displayed of amalgamating with mercury, he de- 

 vised his experiment of the 19th. He took a small glass tube, about the 

 size and shape of a thimble, into which he fused a platinum wire, and 

 passed it through the closed end. He then put a piece of pure potash 

 into this tube, and fused it into a mass about the wire, so as entirely to 

 defend it from the mercury afterwards to be used. When cold, the potash 

 was solid, but containing moisture enough to give it a conducting power ; 

 he then filled the rest of the tube with mercury, and inverted it over the 

 trough: the apparatus being thus arranged, he made the wire and the 

 mercury alternately positive and negative ; and now, conceiving that I 



