JOURNAL' 



OF 



NATURAL PHILOSOPHY, CHEMISTRY, 



AND 



THE ARTS. 



NOVEMBER, 1808. 



ARTICLE I. 



Observations on the Exhausting Machine of Dr. Thomas 

 Stewart Traill, by Mr. Robert Bancks, Mathema- 

 tical Instrument Maker, in the Strand. 



I 



To Mr. NICHOLSON. 

 SIR, 



N the present enlightened state of science, it is not to The same 



be wondered, that different scientific men should have simi- 'hings thought 

 .,'•11, ,. . • . 1 of by diffeient 



lar ideas, with the hopes oi constructing mstrumentsm the persons. 



utmost state of perfection. I am led to this reflection by a 



description of a machine, in your Journal for last month, 



nearly similar in construction to one made by me ten years 



ago for Bracey Clark, Esq., a gentleman well known in the 



scientific world. 



After some ingenious observations by Dr. Traill, on the Air pump. 



impossibility of obtaining a perfect vacuum in the air pump 



of ordinary construction, he says, p. 63, " it occurred to 



me, that, if there was a convenient method of using the Torricellian 



Torricellian vacuum, it would be preferable to the common '*^cuumsug- 



1 o gestcd for it, 



air pump, even when best constructed. After various at- 

 tempts, the annexed figure and description will give an idea 

 Vol. XXI. No. 93— Nov. 1808. M of 



