504* To CORRESPONDENTS. 



THE ingenious infimment of I. S. F. for explofions has not 

 appeared to the Editor to be wanted. Chemical lecturers in this 

 metropolis ufe a fmnll particle of pfiofphorus, of the fize of a 

 pin's head, and fprinklc upon it a pinch f /he oxi/m/riate of pot- 

 afh, in a Wedgewood'i nmrtar. ThisfmdU quantity, being Jjt'ruck 

 by a Jltdden rub of the peftle, gives a loud cxphfion with the vifible 

 flame, but the burning matter h too little to endanger the fpecla- 

 tors. 



The excellent perfpective inftrument defcribed and drawn by the 

 Rev. Wm. Gregor, has n •; doubt the priority in aclual date to 

 that of R. L. Edgworth, Efq. defcribed in our firft Vol. page 

 281. But he will fee, by turning t» that article, that the injlru- 

 ments are too nearly alike to admit of a ftcond publication. 



1 am much obliged to Mr. Cumberland for his favour of 

 the llth Eeb. The ufejul nltye&s mentioned in his p ftfeript ap- 

 pear to vie to he fuch as "would be very acceptable to the public. I 

 am afraid that the circumfiance of the invention of Mr. J. having 

 been publiflied before would make it le/s proper to be reprinted in 

 a Journal which is honoured lonli fo much original matter, that 

 prejfesjo>- infertion. But I /hail be ha py to give it a more deli- 

 berate confide ration if his friend will favour me -with the loan of 

 the plates, and fuch additional obfervations or notes as he may 

 think Jit to muke. 



The cafe of deafnefs, communicated by Mr. Hill of Wells, 

 Norfolk, in ivhi'h Jo much benefit zvas derived from electricity, is 

 very inter cfiing. Some medical cafes have ap eared in the early 

 numbers of the firft feries of this Journal; and others prefented 

 themfelves for my decifon as Editor ivtth regard to their value 

 and importance. But in the attempt to perform this part of my 

 duty. 1 found difficulties fo great, and afuhjecljb extenfive, that 

 it appeared proper to confine the papers, to be admitted, to fuch 

 as are directly and immediately connected with chemical and me- 

 chanii al fcience. I jhall be happy to convey his letter to a re- 

 Jpcclable Medical Journal, if he Jhould think fit. 



I am very Jbrry that the letter from a Correspondent,ii7w 

 reqr.ejUd fome enijuiiies to be made, concerning the fundamental 

 experiments on heat, of the late Dr. Irvink, has been fo long 

 without its efij'ett. I hope to be enabled to give the narrative he 

 requefis in the next number. 



