A Letter to Professor Jameson. Payee 
the outer vessel to contain water, which surrounds the other and 
lies under its bottom; or, in other words, this part of the ap- 
paratus consisted of a vessel of tar set into a vessel of boiling 
water. The tar vessel being riveted to the cover, holes are made 
through its sides near to the cover, to allow the steam to pass in 
and to act on its surface. The cover being secured on, a safety- 
valve is provided for the steam vessel; and two cocks, one over 
the tar, the other over the water (but both having communica- 
tion with the eduction pipe), are fixed contiguously ; the first has 
a tube, or is elongated to reach nearly to the bottom of the tar, 
which ascends this pipe when pressed on by the ’steain, and is 
driven forward into the eduction pipe, when the cock over the 
tar vessel is opened for its escape. When both cocks are opened, 
both tar and steam are emitted at onee, and in mixture, through 
the eduction pipe. In this tube (which is for convenience fur- 
nished with two joints) is placed a large wire or metallic rod, 
which about fills the tube, and is perforated obliquely or zigzag, 
to increase the length of the passage, and to mingle the tar and 
steam more intimately. The gases or vapours issue from a small 
orifice at the end of the pipe ; and being ignited by a little fire 
into which it is directed, an intense and voluminous blaze is pro- 
duced, and continues as long as the materials remain unexhausted. 
A hot brick instead of the fire answers the same purpose, 
“ The apparatus contained but about one quart of tar (which 
must always be nicely strained), and it lasted an hour and a half; 
and the flame was sufficient to fill a common fire-place, if not al- 
lowed to escape by its violence up the chimney. Its force will 
be according to the elasticity of the steam. Probably a form of 
stove may be devised wherein it may be used for the purposes of 
warmth, light, and cooking ; and another apparatus to light 
streets. But this invention will be of more special use as fuel for 
sleam Res rien to navigation.’ 
XLVIII. 4 Letter to Professor Jamuson, by Mr. JoHn Farry 
Sen. * 
Sir, — I sxc to take the liberty of mentioning to you, that I 
have this day read, in vol. II. part ii. of the “ Memoirs of the 
Wernerian Natural History Society,” your Introductory Paper to 
an account of “ the Geognosy of ihe Lothians,” which was read 
before that Society on the 17th of December 1814, and now lately 
has been published : in which Paper, at the top of p. 621, oc- 
cur these words, viz. ‘* Mineralogists, in general, distingtish two 
* Communicated by Mr. F., with a request that it should be inserted in 
the Phil. Mag.—Eprror. 
$2 red 
