140 Ori the Effect of Vapour on Flame. 



" In the high mountains on the confines of Glamorganshire and 

 Brecknockshire, near Yueskedwyn (p. 38) I observed a rock of 

 the same kind of black shelly Marble, that is found in such plenty 

 near Kilkenny in Ireland ; and which I afterwards saw in great 

 abundance in Pembrokeshire, where it is also worked. The pe- 

 trified shells contained in all these Marbles, are striated conchce 

 anomice, which are not only exotics, but known to be extremely 

 scarce." 



XXIII. Ore the Effect of Vapour on Flame. By J. F. Dana, 

 Chemical Assistuvl in Harvard University, and Lecturer on 

 Chemistry and Pharmacy in Dartmouth College.* 

 To Professor SiUiman. 

 . Cambridge, Mass. February 5, 1819. 



Dear Sir, — About a year since I made some experiments on 

 theeflfect of steam on ignited bodies, with a view to learn the 

 theory of the action of the " American water-burner." These 

 experiments were published in an anonymous paper in the North 

 American Review, and have been published in London, without 

 an acknowledgement of their source. 



The effect of them concerning bodies is peculiar, and it pro- 

 bably admits of more extensive application to the arts than in the 

 above named instrument alone. 



When a jet of steam, issuing from a small aperture, is thrown 

 on burning charcoal, the brightness is increased if the coal be 

 held at the distance of four or five inches froin the pipe through 

 which the steam passes ; but if the coal be held nearer, it is ex- 

 tinguished, a circular black spot first appears where the steam is 

 thrown on it. The steam in this case docs not appear to be de- 

 composed, and the increased brightness of the coal depends pro- 

 bably on a current of atmospheric air, occasioned by the stearn. 

 But when a jet of steam, instead of being thrown on a single 

 coal, is made to pass into a charcoal fire, the vividness of the com- 

 bustion is increased, and the low attenuated flame of coal is 

 enlarged. 



When the wick of a common oil lamp is raised, so as to give 

 off large colun)ns of smoke, and a jet of steam is thrown into it, 

 the brightness of the flame is increased, and no smoke is thrown 

 off. 



When spirits of turpentine is made to burn on a wick, the 

 light produced is dull and reddish, and a large quantity of thick 

 smoke is given off; but when a jet of steam is thrown into this 

 flame, its brightness is much increased; and when the experiment 

 is carefully performed, the smoke entirely disappears. 



* From Silliman's Journal, No. 4. 



When 



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