Dtfcription of a new Veniilaior. i 



periment, which would not be attended with too much inconvenience. This I have ef- 

 feded by the inftrument of which I now fend the draft and defcription ; and I found the 

 refult of the experiments made with it, fully to anfwer my expedations. 



In the draft the firft figure reprefents the external appearance of this inftrument, and 

 the fecond fl-.ews it in feaion. Plate i. From A to B in fig. 2, there is a free open com- 

 munication in the larger tubes. The part C E D is an open truncated cone, ending in a 

 tube E F, one third of the diameter of that which furrounds it, and which reaches into the 

 larger tube the length of two of the diameters of the latter. 



There it a fcale with the draft for fig. r and 2, which marks the proportion of the fmall 

 inftrument I had firft made. But as the fize of any other muft vary according to* the ufes 

 for which it is intended, I have only fet down the number of proportional parts, and have 

 not mentioned their value, which may be encreafed at pleafure. 



In ufing this inftrument, the bafe C D of the cone muft be turned towards the wind, 

 which when it blows even moderately, will then caufe a very fenfible current of air to pafs 

 up from A to B through the larger tubes. The fmall inftrument, which I tried at a time 

 when the wind was low, when placed as above diredted, oppofite the opening of the upper 

 fafh of a window let down about two inches, a£ted with fuch power, as to draw the flame 

 of a candle'confiderably into the tube A, held horizontally at fome diftance from it, and 

 made the tube B, by which I fupported it, fo hot in a fhort time, that it was painful to 

 hold it. 



This experiment I repeated before many gentlemen always with the fame refult ; and 

 which at leaft entitles the inftrument to a trial on a larger fcale for ufeful purpofes, in 

 which I have no doubt of its fucceeding. 



The ufes to which this inftrument may be applied, are of no fmall Importance, even fo 

 far as they have occurred to me ; others may yet be found out which I have not thought 

 of, thofe which I have thought of are as follows : 



ift. It will do extremely well for extracting the unwholefome air from mines, when it 

 is made of a fize fufficicntly large. 



2d. It will alfo be particularly convenient in ftiips for changing the air in them, ren- 

 dered unfit for rcfpiration by the breath and perfpiration of a numerous crew, by the efflu- 

 via from provifions, bilge water, &c. ; and if its efficacy may be judged of in this refpeft, 

 from experiments made on a fmall fcale, it would with a moderate wind entirely change 

 the air in a large veflel in the courfe of two or three hours, even when made of no great 

 fize. 



3d. It will confiderably encreafe the force of tha draft in a blaft furnace, if placed on the 

 top of its chimney as hereafter direfted, for chimneys in general. 



4th. It will fcrve as a ventilator for corn, ftores, magazines, hofpitals, and crowded 

 rooms. 



5th. It is particularly well calculated to prevent or cure the fmoking of chimnies, ( which 



inconvenience frequently renders houfes fo uncomfortable, as to induce the owners to quit 



4 them j 



