96 Griswold on Submarme Explosion. 
as to prevent the possibility of the admission of water to 
the inside. 
It was of a capacity to contain one engineer, who might 
stand or sit, and enjoy sufficient elbow room for its proper 
management. 
The top or head was made of a metallic composition, 
exactly suited to its body, so as to be water-tight; this 
opened upon hinges, and formed the entrance to the ma- 
chine. Six smal! pieces of thick glass were inserted in this 
head, for the admission of light: in a clear day and clear 
sea-water, says my informer, he could see to read at the 
depth of three fathoms. 'To keep it upright and properly 
balanced, seven hundred pounds of lead were fastened to 
its bottom, two hundred pounds of which were so contrived 
as to be discharged at any moment, to increase the buoy- 
ancy of the machine. 
But to enable the navigator when under water, to rise or 
sink at pleasure, there were two forcing pumps, by which 
water could be pressed out at the bottom ; and also a 
spring, by applying the foot to which, a passage was formed 
for the admission of water. If the pumps should get de- 
ranged, then resort was had to letting off the lead ballast 
from the bottom. 
The navigator steered by a rudder, the tiller of which 
passed through the back of the machine at a water joint, 
and in one side was fixed a small pocket compass, with 
two pieces of shining wood, (sometimes called foxfire,) 
crossed upon its north point, and a single piece upon the 
last pomt. In the night, when no light entered through the 
head, this compass thus lighted, was all that served to guide 
the helmsman in his course. 
The ingenious inventor also provided a method for de- 
termining the depth of water at which the machine might 
at any time be. This was achieved by means of a glass 
tube, twelve inches in length, and about four in diameter, 
which was also attached to the side of the machine : this 
tube enclosed a piece of cork, that rose with the descent 
of the machine, and fell with its ascent, and one inch rise 
of the cork denoted a depth of about one fathom.’ "The 
principle upon which such a result was produced, and also 
the mechanical contrivance of this tube, entirely escaped 
