[ 434. ] 



LIX. On the Experiments detailed in Mr. Waldie's Paper 

 on Combustion and Flame, inserted in the Land, and Edin. 

 Phil. Mag. for August 1838. By D. F. Gregory, Esq. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



T ONLY observed yesterday, in your August Number, an 

 •*■ article on the subject of combustion, on wliich, though it 

 be now rather late, I would beg to make some observations. 

 The author of the paper, Mr. Waldie, does not seem to be 

 aware that almost all the experiments which he has there de- 

 tailed were made several years ago, and are well known to 

 chemists, and frequently exhibited in public lectures. They 

 were originally due to that very ingenious chemist Mr. K. 

 T.Kemp of Edinburgh, Chemical Assistant to Dr.Hope, who 

 first performed them in 1833. I do not know whether or 

 not Mr. Kemp communicated a paper on the subject to any 

 of the Journals, but I know that he communicated them freely 

 to other chemists, who as well as Mr. Kemp have exhibited 

 them frequently in their lecture-rooms since that time, so that 

 they must have become pretty generally known. And I am 

 surprised that Mr. Waldie, who seems to have directed his 

 attention to this branch of chemistry, should not have heard 

 of them before this. I may mention that one of the experi- 

 ments, that of burning a jet of oxygen in an atmosphere 

 of hydrogen, I saw performed by Dr. Hope in his lecture- 

 room as far back as 1829 ; but if I recollect rightly, he did 

 not give the true theory of the experiment. Mr. Kemp did 

 this, and illustrated it not only by the experiments detailed by 

 Mr. Waldie, but also by others, which that gentleman does 

 not seem to have tried, such as the burning of chlorate of 

 potass or nitre in an electropositive atmosphere. 



If you think these remarks worthy of a place in your pages, 

 their insertion will much oblige. 



Gentlemen, yours, &c. 

 Trinity College, Cambridge, D. F. Gregory. 



Nov. 3, 1838. 



LX. On a certain Difficidtij connected isoitk the Demonstration 

 (/Euclid, Book I. Prop. 29.* 



A WELL-known difficulty connected with the demonstra- 

 ^-^ tion of Euclid, Book I. Prop. 29, which has long been a 

 stumbling-block in the very threshold of mathematical science, 



• Communicated by the Author. 



