J'46 Oh the EfeSfefa- Mixftift ofTtn nuhh Geld. 



The f-ifegoiftp; are all the paffaoes tliat have occurred to my reading on this fubjeft, 

 'they nrf bu? fevv and incon/iderab'". bat may fave trouble to others, who are willing to 

 make a deeper enquiry into the hiftory of this fubftance. 



Jan. 24> I "90. 



The following pafTage, taken from the Viridarium Franci'ci Mendozz, Sacrae &:Prafan«e Eruditionis. Co* 

 lonis Agrippina;, 16 ; < , (cems to point out, though rather obfcu;ely, the conftruftion and principles of Balloons. 



" V'as aereum, plenam aiire, aiiter dcmergciidura, in fumma aijua fuftentatur, cum ea lit naturahtcr multo 

 gravius ; ergo navis lignea, aut cujuftunque alterius materisE in fummi acris fuperficie conftitiita, et clemen- 

 lari ignc rcplcta, fupraaiirem fuftintbitur, nee prius in ipfo aere fubmergctur, quaiTi navigii gravitas fuperet Ic- 

 vhatem ignis, quo plenum eft." 



Problema XLVII. Utrum ai-r parte aliqua fit navigabilis. W.. F. 



VIII. 



Sxperimtnts and Ohfervations on the EffeB of Annealing a Plate of Metals eonJiJlUig ofjine or 

 ttihytd Gold, uiih one twenty-fourth Part of Tin*. By MatiuW Tillet. 



X. HOUGH the advantage be great, that men of enlightened minds and well known 

 artills fliould make inquiries into the kind of works to which their attention has been par- 

 ticularly applied, and (hould render their obfervations public ; it is neverthelefs true, that 

 their reputation, in many refpedls well founded, does in fome inftances caufc the rcfults 

 drawn from their experiments to be too fpeedily adopted ; and that when they are care- 

 fully repeated, it does not always happen that they prove exa£l. Thefe artifts, no doubt, 

 well informed and faithful in their operations and reports, have not ptetended to offer them 

 as decifive ; but by negleding to confider the fafls before them in every point of view, they 

 have too fpeedily concluded that thefe fads, univerfally confidered, were fuch as to them 

 they appeared at firft. fight. 



Looking over the Journal de Phyfique for the month of September 1788, 1 faw a paper 

 entitled " Experiments and Obfervations on the Fufion of Gold with Tin," which I read 

 with great attention, as being tiie produdion of a man of merit well verfed in his art, 

 namely, Mr. Alchorne, affay-mafter to the Englilh mint. As the objeft of his experi- 

 ments is interefting to every arlift who ufes gold and filver ; as its aim is to remove their 

 fears refpefting the mixture of a certain quantify of tin with fine or alloyed gold, and as 

 thefe artifts do neverthelefs retain their apprehenfions with regard to the fmalleft mixture 

 of tin with the gold of various finenefs, which they are incelTantly melting ; I have thought 

 it proper to repeat the experiments of Mr. Alchorne : and while I admit part of the fafls 

 he has related, I muft refute thofe which my own trials fliew to be erroneous, and which, if 

 they had not efcaped his attention, wouW doubtlefs have led him to make certain excep- 

 tions, in the too pofitive confequences he has drawn from his operations. 



Before I enter upon a detail of the e\-pcriments of Mr. Alchorne, as well as my own, 

 I think it proper to take notice of the manner in which the editor of the Journal announ- 



* Memoirs of the Academy of Sciences at Paris far the year 179Q, bting the concluding volumt, printed 

 in I797' 



CCS 



