34^ Dr, Percival on the Pur/uits 



produce the fpontaneous accenfion of Romberg's 

 pyrophorus, and delivered this opinion to the 

 public, on the evidence of at leaft fifty differ- 

 ent trials. *. Yet, with materials taken from the 

 farrie bottle, the experiment afterwards failid 

 nearly as often, though the minuted circi^|^ 

 fiances in the procefs were as much alike, as 

 attention could render them. Contrarieties, 

 equally humiliating, have often occurred in my 

 own philofophical purluits But the mod in- 

 flrudive Icflbn of modedy and rcferve, which 

 I recolkdt in the courfe of my experience, is the 

 one I (hall now briefly recite. 



The favourable influence of fixed air on 

 vegetation I believed to have been afcer- 

 tained by more than a hundred experiments, 

 which I made in the year 1775- Many of 

 thefe expciiments were repeated afterwards by 

 Mr. Henry, Mr. Bew, and others. But ' Dr. 

 Prieftley, whofe accuracy and fidelity are not 

 lefs diftinguilhed than his learning and inge- 

 nuity, has fince drawn conclufions from the 

 profecution of this fubjcdl-, which militate 

 totally with mine. I refumed the enquiry, and 

 engaged feveral of my friends in it. The 

 refult of all our trials was uniformly the fame 

 as before, viz. that fixed air, in a due pro- 

 portion, is fo favourable to vegetable growth, 



* See Prieftley on Air, vol. HI. Appendix, p. 395. 



that 



