TAA STORRS AGRICULTURAL EXPERIMENT STATION. 
the groove with use, so that the washers have to be replaced 
occasionally. With an instrument devised by Prof. Hempel a 
new washer can be cut out of a thick sheet of lead and inserted 
in a short time. We are, however, trying a washer of copper 
which will not flow so easily. 
One difficulty in screwing the collar down tightly enough to 
prevent the escape of gas between the edge of the cylinder and 
the washer at the high pressure to which the gases are subjected, 
has been the friction of the collar upon the cover. ‘To accomplish 
this the cylinder of the bomb is put in a clamp, which is fitted to 
the cylinder and is held inavise. ‘The collar is turned bya long- 
handled spanner, the projection of which fits into the two depres- 
sions shown in the collar. Even with a spanner handle nearly 
three-quarters of a meter in length, much force is needed to secure 
tight closure. To avoid the friction between the collar and the 
cover, ball-bearings (K K) of very hard steel, such as are em- 
ployed for bicycles, are used in the last bomb made. These run 
in a groove in the cover and are kept from falling out by a flat 
ring which is easily removed. The bearing in the collar which 
comes against them, as shown in the picture, is also of hard steel. 
The platinum wires, H and I, inside the bomb, serve to hold a 
platinum capsule containing the substance to be burned and to 
transmit an electric current. Of these two wires one, I, is 
screwed into the cover; the other, H, passes through a conical 
hole in the cover from which it is insulated by a piece of vulcan- 
ized rubber, in the shape of a frustum of a cone and fits the 
hole. A small nut screwed on the platinum wire at the upper 
surface of the cover draws the wire and with it the vulcanized 
rubber cone tightly into the hole and holds them in place. Near 
the lower end of H is a platinum wire bent in the form of a ring 
to hold the platinum capsule and coiled about the wire, to which 
it is held by a screw. When a combustion is made the two 
platinum wires are connected by a very fine iron wire which 
passes over the crucible. The part directly above the substance 
to be burned is bent into a spiral, thus furnishing a larger 
quantity of iron to be ignited and, falling, to ignite the substance 
in the crucible. The cylinder is approximately 12.5 centimeters 
deep and 6.2 in diameter inside. The wall is approximately .5 of 
a centimeter in thickness. The weight of the whole bomb is 
approximately 2,900 grams and its capacity nearly 380 cubic 
centimeters. 


