STOWAGE OF SHIPS. 209
the wood must be of a good kind, and the casks oughtto be correctly made.
In the arrangement of the objects forming the cargo ofships, it is very often required to stow a great number ofcasks in tiers one above another, AB, CD, EF, fig. 21.The separate tiers, when not above three, are called theground tier, middle tier, and upper tier; when abovethree they are numbered, the lower one, or No. 1, being,however, still called the ground tier. It is of great im-portance to know beforehand the height of each tier, inorder to ascertain what portion of the hold of a ship willbe occupied by the casks of wine, water, and spirits whichshe is to take on board, and, of course, what space willremain for the rest of the cargo.*
Though the combination, fig. 21, produces a gain of27 hundredths of the radius of the casks, there is a con-siderable space lost, which is avoided by the modern me-thod of keeping the water on board ships, in iron tanks ofa cubical form, adapted to every part, even the most irre-gular, of a ship’s hold. The metal, moreover, is better forpreserving the water sweet than the wooden staves.
In arsenals, whether for the service of the army ornavy, cannon balls, howitzer and bomb-shells, grenades
* It should be observed, that the three barrels m, n, p, supposedto be equal in size, all touch each other in the lines joining their cen-tres ; therefore, the centres are at a distance from each other equal tothe greatest diameter of the barrel. Let the right line nh, in thetriangle mnp, be drawn from the summit n, perpendicular to mp, mak-ing mh — hp = 1, we shall have mn — 2; and because the square ofthe hypothenuse is equal to the sum of the squares of the other sidesof the triangle, we shall have nh" ~ mn 2 — mh 3 = 4 — 1 = 3.
From this we see that nh is nearly equal to 1,73. But the centresm, p, are at a distance from their support equal to the radius of thecask = 1, consequently, the height of the centre n, above the sup-port, is 2,73.
If the cask n, was placed directly over the cask p, the height ofthe centre n, above the support, would be three times the radius;consequently, the sinking of each range of casks into the hollowsbetween the casks of the range below, causes a gain of nearly twenty-seven hundredths of the radius
P