20 BULLETIN 379, U. S. DEPARTMENT OF AGRICULTURE. 
der as shown at B, and also from beneath the fan as shown at C, there 
being another connection on the opposite side of the fan from C. 
The method of installing the fan necessarily will-vary with the. 
type of separator. The object is to remove the dust from near the 
cylinder. The fan should be arranged to accomplish this. 
There is no way of demonstrating by experiment that either of 
these methods actually prevents explosions, but the fact that no 
such occurrences took place in the case of separators properly 
equipped with either one of these devices, while explosions and fires 
were constantly occurring in machines located near them and not 
so equipped, warrants the belief that the devices proved effective in 
preventing explosions and consequent fires. 
AUTOMATIC FIRE EXTINGUISHER. 
Experiments conducted in the field during the threshing season, 
and since that time on the Arlington Experimental Farm at Ar- 
lington, Va., show that, under ordinary conditions, it is very diffi- 
cult to secure a fire in a separator by the introduction of matches 
or other foreign materials. This has been particularly the case 
in experiments conducted on the Arlington Experimental Farm, in 
which, owing to the lack of smut dust and proper atmospheric con- 
ditions, it was impossible to secure an explosive mixture in the 
separator. In order to set fire to the separator in these experiments, 
it was necessary to introduce a flame and, to secure positive results, 
use was made of waste and rags soaked in gasoline and ignited by a 
flame from the outside. Bundles of matches fed in with the straw 
did not cause a fire. 
However, since there is a possibility that fire will be caused under 
certain conditions by the entrance into the separator of foreign ma- 
terials, and since it was impossible to prove positively that either 
grounding the separator or the use of the suction fan was a sure 
preventive of fires, it was decided to design an automatic fire extin- 
geuisher that would afford protection irrespective of the cause of the 
fire or explosion. Such a device is shown in Plates X and XI. It 
consists of the following parts: Tank A mounted on top of the sepa- 
rator; within the tank a bottle, C, containing sulphuric acid; a dis- 
charge pipe, H; a tripping mechanism composed of operating levers 
G and main tripping lever L; a trigger, N; discharge nozzles, I; and 
fuses, F, mounted in a wire line. In the discharge line between the 
tank and the separator may be mounted a three-way valve, P, from 
which there may be led, as at R, a hose connection for extinguishing 
outside fires. The tank is filled with water containing soda. The 
operation of the device is as follows: 
The presence of sufficient heat within the separator will melt one of 
the fuses F. This breaks the wire line, releasing the trigger which 
Ee 
