280 0« a new Mode of preparing 



tain a fresh supply of the vaccine matter early in the spring, the 

 inoculation for it will sink into disrepute, and I myself come in 

 for a large portion of the disgrace. Judge of my anxiety when 

 I say, that I am conscious that more than an hundred prac- 

 titioners in different parts of New England are at this time in- 

 oculating with spurious matter, while the small-pox is pervading 

 Oiie of our sea-ports, and every unfortunate case will be traced 

 up to me the originator of the practice in America. 1 am the 

 only ))erson who ever succeeded in obtaining efficient matter 

 from England, which I had from Dr. Havgarth, and the activity 

 of this matter seems worn out by passing t/iruugfi a inimher of 

 the human species; and unless I obtain a fresh supply from Eng- 

 land, the business which promised so fair here will stagnate. I 

 have, therefore, written to Dr. Jenner for his advice and assist- 

 ance. So I have to Dr. Pearson, and hope, by the return of the 

 Galen, or by the Minerva, to get a supply of the matter I stand 

 so much in n^ed of. I have just received an order from the 

 War Department, to supply the military surgeons with the vac- 

 cine matter, and directions for inoculating the different corps of 

 artillerists and engineers eniployed in the various parts of New 

 England." 



Dr. L. to Dr. IV. 

 London, Mar. 28, 1800. " Sent him fresh cow-pox matter." 



Dec. 24. " Sent him vaccine matter in a glass bottle, 

 from the Vaccine Institution, as well as two planes 

 of glasses, one from Dr.Wuodville and the other from 

 Mr. Johnson. Explained Dr. Woodville's, Dr. Pear- 

 son's, and Dr. jenner's opinions, respecting the 

 wearing out of the effect of the matter." 

 Feb. 19, ISOl. " Sent him vaccine matter in a glass 

 vessel from mvself, with a letter and vaccine matter 

 from Dr. Pearson." 

 I have honour to be, sir, your very obedient servant, 

 Bolt Court, rieet Street, April 16, 1817. T. J. PettiGREW. 



LXX. On n nciv Mode of preparing arsenical ed HydrogenGas j 



%vitk the last Experiments of Gehlen on this Subject, 



[The cxpeiimeiits wliicli this paper aiinounccs, possess a peculiar interest, 



from the melnncholy iate of the cxptiinirntcr, i\J. Gelikn, who fell a vic- 



tlu) t/) the flelittrioab eifects of the t;a=i, the constituents of which he was 



analysing. Tlie account of thi;in which foHows, has been made up from 



the niemoranciums iie left behind hini ; and the observations which are 



_ addeil are from the pen f)f the ingenious M. Gay Lussac * ] 



An order to ascertain how arseiiic is affected by caustic potasb, 



M. Gehlen put 200 grains of arsenic along with three times as 



* From the Annales de Chimie el de Fi'it/sii]ue, for October 1816. 



much 



