328' Mr. Palte.n's Air Pum-p. 



which the air pump can be immediately converted into ar 

 condenser ; the construction of the stop-cock is, I appre- 

 hend, not perfectly understood by Mr. P. ; and although 

 he considers the suggestion of it as " a substitution 

 ahogether useless," and " an awkward alteration'' of his 

 own contrivance, yet there are other gentlemen who perhaps 

 may differ from Mr. P. in opinion on this sal»ject ; but after 

 all, the merits or demerits of the proposed improvement 

 must r(;st, not on opinion, but on its practical ulilili/, and 

 on that I am entirely willing that it should stand or fall. 

 Perhaps something similar to this may have been suggested 

 before; there have been numerous inventions to dispense 

 with valves ; and the contrivance may have been thrown 

 aside as useless, thus sharing the fate of many mercurial air 

 pumps. 



As to the "insinuated charge of borrowing," I am not conscious 

 of having made that insinuation myself, but I am conscious 

 that none was ever intended by me, as I am determined that 

 my remarks shall ever be governed by courtesy and candour. 



It does not diminish the credit of Scheele that, without 

 any knowledge of what had been done, he should have dis- 

 covered oxyg<.*n gas after its discovery by Priestley; and, 

 "parvis componere magna," it is not, perhaps, disreputable 

 to me. without any communication, directly or indirectly, 

 with Mr. P., to have entertained notions about an air pump 

 similar to his own, even "several months," or "several 

 years," after he had conceived them ; nor does it, I con- 

 ceive, diminish aught of the praise to which Mr. P. is entitled, 

 that another individual should have had similar notions to 

 those he possessed. 



As soon as the practicability of Mr. Patten's air pump is 

 established, I shall endeavour to avail myself of its use, and, 

 whether fuinished or not wiili the " awkward alteration,'' 

 shall cheerfully give him the whole credit to which he is 

 entitled. 



There is certainly nothing remarkable in the fact that two 

 persons, " at no inconsidorabie distance from each other,'' 

 having the same object in view, should adopt similar means 

 for attaining it. There are not wanting instances of per- 

 sons, living in different countries, and at different periods of 

 time, attaining the same object by similar methods, and that 

 too without any concert, or any knowledge of a prior inven- 

 tion: this last remark is probably applicable to the ^'balance 



