568 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
in the head a, which is well screwed on against a shoulder or face armed with 
a collar of leathers. 06 is the hole for admitting common air when the piston is 
drawn quite back. The manner of working consists simply in pressing the 
end of the rod of the charged syringe strongly against the ground so as to drive 
the air suddenly on the tinder, and the cap a@ being without loss of time 
unscrewed the tinder is found to be on fire. 
Tt will be noted that this instrument differs in one important 
particular from the ordinary fire piston of the physical laboratory. 
In the latter the air is merely compressed in the bottom of the cylin- 
der, whereas in Lorentz’s machine the air is not only compressed by 
the drive of the piston rod, but it is also forced under high pressure 
through a minute duct beyond which the tinder les. The term fire 
syringe, so frequently applied to the various instruments for pro- 
ducing fire by air compression, seems to be peculiarly suited to this 
form, since the air is forced through a duct at the end of the main 
cylinder chamber, just as water is forced through the nozzle duct of 
a squirt or syringe. No doubt the air, already heated by the com- 
pression, gains additional heat from the friction caused by its violent 
passage through the small duct. It is possible that this instrument 
owes its origin to the observation of the flash produced by the dis- 
charge of an air gun, to which I have referred above, in addition to 
the scientific experiments as to heat generated by simple compression 
of air in a small space. 
Fire pistons in which the duct was omitted appear to have enjoyed 
some favor upon the Continent, and to a lesser degree in England, 
during the early third of the nineteenth century. In the Mechanics’ 
Magazine, Vol. XVII, 1832, p. 328, the following passage occurs: 
The following is a sketch of a simple instrument for obtaining a light. As 
the invention, though not new [it is very well known on the Continent by the 
name of the instantaneous light-giving syringe. AS it has not, however, been 
described in this work and may be new to some of our readers, we insert our 
ecorrespondent’s description.—Editorial note], is, perhaps, not generally known, 
I shall be glad to see this description of it in your magazine. * * * Yours 
respectfully, E. J. MITcHELL, June 19, 1832. 
The description referring to the figures (fig. 2) I give in full: 
AB is a brass cylinder, similar in appearance to a small brass cannon, having 
the hole rather better than three-eighths of an inch in diameter, drilled true and 
clean rinsed. cp is the form of a piston to work in the cylinder, but unpacked. 
EF is the same ready packed with thick leather and fitted up for use. H is a 
circular brass nut, working against the screw to keep the packing tight. kK isa 
small hook, fastened in a hole drilled through the nut H. c is the handle to the 
piston and is made of wood. The method of use is described as follows: ‘“ Pre- 
pare some thin cotton rag (older and thinner the better) by steeping it in a solu- 
tion of saltpeter, and drying it in a warm oven; tear a small piece off and place 
it on the hook kK; introduce the piston EF into the cylinder Aas a short distance 
only; then take the cylinder in the right hand, place it perpendicular upon 
the floor or a table, and strike the handle © with the ball of the right hand, so 
