393 
CARS DRIVEN BY CONDENSED AIR. 
scratchincf as well as marble. Tbe reenipt is 
as follows: — I'o one pmi of spirits of wine, 
ad'l half an ounee of pum slultack, tialf an 
ounce of gnm lack, lialf an onn'-e of gum 
sundrick; olacing it over a gentle heat, fre- 
quently agitating it until the gums are dissolv- 
ed, when it is fit tor use. iN'Jake a roller of 
list, put a litile of tlie polish upon it, and co- 
vet that with a soft linen rag, wdiudi must be 
sdgh'ly touched with cold-drawn linseed-oil. 
Ruh the wood in a circular direction, not 
covering too laige a space ai a time, till ihe 
pores of the wood aie sntficienily filleil u:>. 
After this, ruh in the same manner -pints of 
wine, with a small portion of the polisli adrl- 
ed to it. and a most hiiiliant polish will be 
produced. If the outside has been previously 
polished with wax, it will he necess-jrv to 
clear It off' with glass paper. — Amer}C in Rnil- 
road Jouniul. 
SLAl'E TOP FOR WASH HAND 
Sl’ANDS. 
Sir, — The Caernarvon ulue slate, like India- 
ruhiier, is used for vmious purposes. Could 
it not he used for the table part of wash-hand 
Blands {* Not that il would he as beautiful as 
white marble, but that it wouLl be handsomer 
than painted wood, with the paint hall washed 
off, which is too oiten the case wn/i tli.it arti- 
cle of furniture. After polishing tlie slate, 
were figures cut in it, possibly it might be 
made to retain paint; or a kind of mosaic 
work might lie made of it f y inserting pieces 
of white mande in it ; or other means might 
be useii to ornament il. 
Yours, &c. 
An Amateur Mechanic. 
OBTAINING A POWER FOR PROPEL- 
LING CARS, BOATS, &c. 
Alexander M’Grew, Cincinnati, Ohio. 
— My improvement does not consist in the 
employment of any newly-invented machine- 
ry, but in the using of such power from falls, 
or currents of water, or other natural or ar- 
tificial sources of power, as has heretofore 
been allowed to run to waste, and employing 
the same for the purpose of condensing of 
air into suitable receivers ; the elastic force 
of which condensed air is to be subsequently 
applied to the purposes herein designated. 
In numerous situations in the courses of 
canals and railroads, and of other roads and 
water courses, there are falls of water, waste 
weirs, dams, sluices, &c., the power from 
which, if economised, would be ample for 
the attainment of all the ends proposed by 
me ; I bring this into use by taking the 
waste power from wheels, or other machine- 
ry already erected, or by erecting others 
where they do not already exist, using any 
• Tbis •ripplicalion of slate has alieady been made 
by Mr. fctiiliiig- See Hlech Mag. p. 231. 
of the known constructions of such wheels, 
or other machinery, as may be best adopted 
for the particular situations in which they are 
to be employed ; these 1 connect in the ordi- 
nary way with the piston, or pistons, of con- 
densing engines, constructed for the condens- 
ing of air, and force air thereby into suitable 
receptacles, or reservoirs, furnished with the 
requisite tubes, valves, or other appendages, 
by which they are adapted to the containing 
of the air thus condensed, and the supplying 
of the same in measured quantities, so as to 
Operate upon a piston for driving and propel- 
ing machinery, as high steam is now made 
to operate. The means of doing this does 
not require any description, being perfectly 
familiar to competent engineers. The air is 
to be condensed into one large stationary 
reservoir, and, by means of a connecting-tube 
and stop cock, transferred therefrom into 
other reservoirs connected with the vehicle 
to be propelled. What 1 claim as my im- 
provement in the art of propeding cars, boats, 
or other vehicles for transportations, is the 
employment of the waste power of water, 
wind, or other natural or artificial sources of 
power, to the condensation of air, in the man- 
ner, and for the purposes, hereinbefore set 
forth. 
REMARKS BY DR. JONES. 
It has been repeatedly proposed to drive 
railroad -cars, &c,, by means of condensed 
air, instead of by steam, and to erect station- 
ary engines for the purpose of filling the 
requisite reservoirs, and we believe that the 
thing was attempted in England. Were 
there not serious practical objections to the 
plan, it would certainly present many advan- 
tages, but these are so weighty, that they 
are not likely to be removed. Among them 
is the perpetually diminishing power of the 
condensed air, as every stroke of a piston 
must lessen its elastic force ; to graduate 
the quantity emitted from the reservoir, in 
proportion to this diminished force, would be 
very difficult ; and, besides this, there ought, 
when the reservoir is renewed, to be apressui’e 
of several atmospheres above what is requir- 
ed in a steam-boiler, or it will soon be so far 
exhausted as to be inadequate to the produc- 
tion of the intended effect, as they would 
have to be exchanged whilst under a pressure 
of two or three atmospheres. 
The present patentee does not propose to 
remove the foregoing, or any other objection 
to the use of condensed air, excepting it be 
the necessity of erecting stationary engines 
to effect the condensation , and to accom- 
plish this, he depends upon the employment 
of means which would generally be more 
difficult, precarious, and expensive ; in many 
places, the means of condensation proposed 
to be used would not be found within many 
miles of the stations where the reservoirs 
would be wanted, and there are, in fact, but 
few situations where the means of applying 
waste power would not be a costly under- 
taking. 
