on Photogenic or Hydrocarbon-Oils from Coal. 113 
in this article. Our attention will be pen per ron ae to the first chapter of 
Dr. Antisell’s book—* History of the Art”—for e errors which have too 
long been current in the annals wo. rca reap pa , the eds ova of 
which by our author is the more ardonable, since, from very position, 
he should have known them to be anil Indeed, from statements ‘a be found 
in various parts of his work, it would appear that he must have known of these 
errors—that he must have been in possession of most of the facts ‘which will 
here be Reuas forward. 
That may form a correct notion of the subject under discussion, let us 
here ‘gress for a moment. 
general rule, when any bituminous substance is subjected to distilla- 
rons i ordinary acceptation of the term, 7. ¢., when it is ccm heated 
in any appropriate appar atus, a quantity of an oily fluid is produced, which 
may be collected in er gc smal] quantities of gas, water, and ats inci- 
dental products being at the same time obtained. 
a std Jiquid, which sone interests us here, known in this country as 
, is a mixture of various hydrocarbons, among which the wax-like 
Pin Pest ne is an almost never-failing constituent. Crude oil, thoug 
of course varying greatly, according to the sources a which it is ‘derived, 
like the various marketable “coal oils” obtained from it by purification, is spe- 
pl centerined by its low specific gravity, being capable of floating upon 
"When n, on the other hand, a bituminous substance, — of naee — 
and gradually heated, is sudden nly exposed to the action of an intense hea 
when, as in.the o rdinary process of pact pee ta it is thro own into v siete of iron 
: hydro 
heavier than water. These co aise coal-ta: ye “ante them paraffine is 
longer found, excepting in compar atively ine instances, another solid mead 
: stance, Naphthaline, being a c canecues component of the mixture. When 
: € process to which the bituminous Lae is subjected is a mixe ed one, 2.€., 
: when a portion of the substance comes in contact with strongly heated surfaces, 
while other portions receive only ana wis nt of heat sufficient to distill off oils 
of the kind first described, a mixed product, containing both coal-oil and coal- 
t im ; t 
Suited for oas-ma t of the great amount of heat which is ren- 
dered latent by Abb ,ehormous volume of gas generated by this highly bitu- 
inous substa 
should be e coal-oil and coal-tar contain a quan- 
lity of “light be meitonea "4 pe esr ‘ exceedingly volatile and inflammable 
liquids, Some of these naphtha-like fluids, for example benzo the ona of 
prea n as benzude in the private vocabulary f Dr. Antisell, or that 
of his proof-reade —may th in crude- din tar; oth i 
“r to these “ light-stuffs” here merely fo urpose of explaining that t ey 
have been at times spok « yolatile oils,” from the resemb] c 
nsiderately 
that Dr. 
obscured his edeal HEN = ae of the art of ‘stilling scala 
a ceaeuridge and allied 
* In the e class are several Scotch cannels, our ai cama and allied 
foals, also the & Divert ¢ oal of New Brun es 3 oe 
SECOND SERIES, Vox. XXX, No. 88.—JULY, 
15 
