74 aie O'R Foe 
pected operation. If the fame thing fhould be attempted: 
with this vafe ftove, it will be well for the buyer to ex- 
amine thoroughly fuch pretended improvements, left, be- 
ing the mere produCtions of ignorance, they diminifh or 
defeat the advantages of the machine, and produce incon- 
venience and. difappointment. 
The method of burning fmoke, by obliging it to defcend 
through hot coals, may be of great ufe in heating the 
walls of a hot-houfe. In the common way, the horizon- 
tal paflages or flues that are made to go and return in thofe 
walls, lofe a great deal of their effe&t when they come to 
be foul with foot ; for a thick blanket-like lining of foot 
prevents much of the hot air from touching and heating 
the brick work in its paflage, fo that more fire muft be 
made as the flue grows fouler: But by burning the fmoke 
they are kept always clean. The fame method may alfo: 
be of great advantage to thofe bufinefles in. which large: 
coppers or caldrons are to be heated. 
Written ai» Sea, 1785.. 
N° VII. 
A Theory of Lightening and Thunder’ Storms, by ANDREW. 
OxivER, E/q. of Salem in the State of Maffachu/etts. 
ao a T has been generally, and, confidering the phe- 
He nomena themfelves, very naturally fuppofed, 
that the electric charges which are exhibited in repeated 
flathes of lightening during.a thunder ftorm, are previoufly 
accumulated in the vapors which conftitute the cloud; and 
that thefe vapors, when by any means they become either; 
over-charged with cleric matter, or are deprived of their 
natural 
