Hare’s Gasometer. 313 
first; so det the length of the arm A, be to the length of the 
arm rom the centre D, with the radius A, describea 
circle ; on which set off an arch C, equal to the whole 
height through which the Gazometer is to move. Divide 
this into as many parts as there are spaces in it, equal each 
to one-sixth of the radius or length of the arm A. Through 
the points thus found draw as many diameters ; which will, 
of course, form a corresponding number of radii and divis- 
ions, on the opposite side of the circle. Divide the differ- 
ence between the length of A and B, by the sum of these 
divisions : and let the quotient be g. From the centre D 
towards the side E, on radius 2, set off a distance equal to 
the length of the arm A, less the quotient org. On radius 
3, set off a distance equalto A, less 2 qg, or twice the quo- 
tient ; and so set off distances on each of the radii ; the last 
being always less than the preceding, by the value of q. 
curve line bounding the distances thus found, will be that of 
the arch head E. The beam being supported on a gudgeon 
at D, let the Gasometer be appended at G, and let the 
weight be appended at F,, adequate to balance it at any one 
point of immersion. This same weight will balance it at all 
other points of its immersion—provided the quantity of water 
displaced by equal sections of the Gasometer be equal. 
But as the weights on which A and B were predicated, may 
not be quite correct, and as, in the construction of large ves- 
sels, equability of thickness and shape cannot be sufficiently 
attained—the consequent irregular buoyancy is compensa- 
ted by causing the weight to hang nearer to, or farther from 
the centre, at any of the points taken in making the curve. 
This object is accomplished by varying the sliders seen op- 
posite to the figures 1, 2,3, 4, 5, 6. When they are prop- 
erly adjusted, they are made firm by the screws of which 
the heads are visible in the diagram. 
The drawing is of a beam twelve feet long; and of course 
the length of the arm A is six feet—that of B four feet—~ 
their difference two feet ; which divided by six, the number 
af points taken in making the curve E. gives four inches for 
uotien 
