VOL. XXVII.] PHILOSOPHICAL TRANSACTIONS. 6] 5 



Query 2. Whether the effluvia or steams proceeding from the red-hot metals, 

 which the air may take along with it in its passage near them, do not very much 

 contribute, if not wholly occasion the effect?* 



If the latter takes place, I presume it may in some measure be applied to 

 account for the effect that the damps, or steams, which arise from subterra- 

 neous caverns, impregnated with metalline effluvia, have on the lives of ani- 

 mals; and yet at the same time, the same air may suffer no change in respect to 

 its other properties, I mean its elasticity and specific gravity, in comparison with 

 other air in the same region. 



Experiments concerning the Effect of Air passed through a Degree of Heat, 

 equal to that of boiling Water. — I contrived a brass box, about 4 inches long, 

 and an inch and half over; at one end, which I soldered up, I fixed two small 

 brass tubes; one of which went through, and reached the remoter end nearly, 

 the other tube was but just inserted in it; but each of them was long enough 

 to reach sufficiently above the surface of the water in which they were to be 

 put. These tubes were to convey the air into a receiver exhausted of its air: 

 it passed first into that tube which nearly reached its opposite end, and so into 

 the other which led to the exhausted receiver. But the box, with that part of 

 the tube that was within it, was first pressed full of brass dust, which I had the 

 conveniency to do by means of a brass cap, which screwed on to the end, not 

 before-mentioned. This brass dust I moistened with a little water, thinking 

 thereby to exert a more than ordinary steam, or effluvia, from the metal, which 

 the air might take along with it, as it passed through such straight and narrow 

 avenues, as it must do between the brass dust. In this manner it was put into 

 the water when cold, and continued in it till it had boiled a considerable time; 

 by which means it must, in all its parts, be of the same degree of heat, at least, 

 as the boiling water. Thus it was taken out, and applied to the exhausted 

 receiver, where, on turning a cock, I gave the liberty for that air only to pass 

 into it, which must succeed through the brass box and dust, under the circum- 

 stances above-mentioned. When the receiver was full of this air, the cover was 

 taken off, and a lighted candle plunged into it, where it continued burning, even 

 at the bottom, as if it had passed through no such medium, but had been full 

 of common air. I took that method to try it, believing the flame of a candle 

 to be the most tender way of discovering a change in air. Afterwards I repeated 

 the same experiment over again, with dry brass dust instead of the former, but 

 the success was the same. It seems, therefore, that such a degree of heat, as 

 that of boiling water, is not sufficient to cause any considerable change, if any 



* The before-mentioned effects of atmospheric air upon animals and flame, after its transmission 

 through red hot metallic tubes, are owing not to effluvia or steams proceeding from the metals, but 

 to the absorption of the oxygen by the metals. 



