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directions, by which the part might be kept in that condition, 
as to cleanliness, most favorable to oxidation. Several 
members thought that the action was owing to galvanic 
currents arising from portions of the iron taking the electro- 
negative condition, which that metal is so apt to assume. 
Professor Roscoe called attention to the pernicious conse- 
quences attending the use of unglazed arsenical green paper 
hangings. His own experience corroborated the observation 
of Dr. Taylor, that dust collected in rooms, so hung, contained 
a large quantity of arsenic. He had analyzed the dust from 
the shelves, &c. of a room occupied by himself, and had found 
a considerable quantity of this poisonous substance. 
Mr. Dyer read a Paper on “ Imponderable Matter, con- 
sidered as an Element” 
He stated, that about tvvo years ago, his first Paper on the 
“ Nature of Heat,” was read before the Society, and he 
therein maintained that the “ Matter of Heat” was not a 
misnomer, but, in fact, a material element, that pervaded all 
space and all bodies in the universe ; and in its neutral state 
was identical with the electrical and magnetic fluids, as also 
with lights or the luminous principle. 
Since then, he had read three other Papers, to illustrate and 
explain his views of elemental heat, and its agency in phe- 
nomena, exhibited by its mutations from the elemental state, 
into and out of the conditions commonly expressed by the 
terms, sensible, radiating, and latent heat ; the present Paper 
being intended to give a summary of the views advanced in 
the former. For the sake of brevity, his own is treated as a 
“heat-force theory,” to denote its being opposed to the 
“ lorce-heat theory ;” and considering that this latter theory 
has been advocated by many eminent j)hilosophers among the 
ancients, as well as the moderns, it would be a great temerity 
in him to oppose that theory, unless lie had some strong 
