354 
tine,) capable of holding about one 
hundred and twenty gallons: into this 
they put forty gallons of the prepared 
tar, and with a gentle heat drive off the 
water and other impurities which the 
tar holds in solution. As soon as they 
perceive the whole of the water is come 
over, and there begins to run a fine 
clear spirit, they stop the distillation, 
and when a little cooled, the pure tar is 
drawn off and reserved for the purpose 
of black-making, to which this inven- 
tion has reference. ‘This purified tar 
thus obtained may be made into black, 
in the apparatus hereafter described, or 
may be subjected to a further rectifica- 
tion to divest it of the mineral pitch or 
asphaltum, which is combined with tle 
pure oil {and spirit; they prefer the 
latter process, as the mineral pitch or 
asphaltum is only inflammable ata high 
temperature, which renders it more 
troublesome to use; the apparatus re- 
quiring frequent cleaning from the car- 
bonized pitch falling to the bottom and 
choaking it up. &n order to get rid of 
the aforesaid mineral piteh or asphaltum 
they proceed as follows: having the 
forty gallons of tar in the still, as be- 
fore described, instead of stopping the 
operation when the spirit begins to come 
over, they continue the distillation with 
a strong heat, and force over the whole 
of the oi] and spirit contained therein, 
leaving the residue asphaltum in the 
still. As the mode of doing this is well 
known {o every person acquainted with 
distillation, the particulars necd not here 
be described, as they form no part of 
the invention, and may be done in any 
still capable of bearing a strong heat to 
which a refrigerator or worm-tub is 
affixed; this patent’ being solely for the 
application of these two produets, name- 
ly, the refined coal-tar and coal-tar 
spirits for the purpose of black-making, 
which, together with the apparatus em- 
ployed, they claim as their exclusive in- 
vention. 
Do Witttam Jessop, of Butterley Hall, 
Derbyshire, Ironmaster ; for an elastic 
metallic Piston, or Packing for Pis- 
ions, to be appiied either externally 
or internally to Cylinders. March 
27, 1823. 
This invention consists in the applica- 
tion of an elastic metallic cylindric ring 
(formed by a spiral of two, three, or any 
other number of circumvolutions, after 
the manner Of a screw), to be used as a 
substitute for hemp, leather, or other 
substances, as packing for cylinders, 
pistons, plungers, rods, buckets, or 
New Patents and Mechanical Inventions. 
[Nov. 1, 
other thing, to prevent the escape of 
steam, air, water, or other fluid, as the 
case may be, as well as to lessen the 
friction thereof, and to increase the 
effect of power on steam-engines, pumps, 
and other machines to which it is 
applied. 
This is effected by making such spi- 
ral cylindric ring of a greater or less 
diameter than the cylindric body against 
which it is to act, so that by its expan- 
siye or contractile power it should en- 
sure the touching and fitting of the sur- 
faces without so much pressure as to 
cause unnecessary friction, The spiral 
ring is to be adapted and fitted in a 
groove or recess, or situation on the 
piston-bucket, stufling-box, or other part 
to which it is applied, which may be 
done by any of the methods commonly 
used and well understood. 
The spiral ring may be manufactured 
by different means, but he bas found the 
following convenient: he makes of 
brass, or other metal or mixture of me- 
tals, of proper quality, a cylindric ring, 
varying in its dimensions according to 
the circumstances of its application ; 
which ring he divides or cuts in a spiral 
direction, on its cylindric edge, into 
two or three, or such other number of 
circumvolutions as may be necessary or 
convenient. 
The power ofa steam-engine, by the 
application of the metallic spiral pack- 
ings, is considerably increased ; this in- 
crease will vary according to the pow- 
ers of the engines, being greater in small 
engines, from their having larger pro- 
portionate surfaces of cylinder. The 
metallic spiral packing was first applied 
to a six-lorse engine, by which the 
power has been increased fully one- 
fourth, and with the saving of one-third 
_of the fuel, and three-fourths of the tal- 
low to the piston. In all engines, to 
which the metallic spiral packings may 
be applied, the saving of fuel will be 
very considerable, and one-fourth only 
of the tallow to the piston will be re- 
quired; they bave the farther advan- 
tage of seldom requiring examination ; 
the loss of time, therefore, and the in- 
convenience arising from the necessity 
of frequently packing the common pis- 
tons, will be avoided, an object of con- 
siderable importance in nianufactories, 
and also to steam-vessels. 
By experiment, the friction of two 
smooth metallic surfaces of iron and 
brass, oiled, amounts only to an eleventh 
part of the weight with which they are 
loaded. In a forty-horse engine the 
metallic 
