202

RULES

FOR MAKING OR CORRECTING THE GAUGE POINTS ON THE ENGINEER'S SLIDe rule.

The Engineer's Slide Rule is an instrument of extensive use to mechanics; and almost every one who is in possession of the rule, is also, or may be, in ample possession of instructions; but I am not aware that any information has been given in any other work, for either correcting the old gauge points or obtaining new ones;-hence, the following may be found useful.

And first, by making the 3rd column on the rule (or that marked III) the first of our observations, renders the others very simple; thus,

The 3rd column is the number of cubic inches contained in a lb., foot, gallon, &c.

The 2nd column is the numbers in the 3rd column, expressed in the decimals of a foot or multiplied by

.833.

The 1st column is the 3rd column divided by 1728. The 5th column is the 3rd column divided by .7854. The 4th column is the 5th column expressed in the decimals of a foot; or, multiplied by .833.

The 7th column is the 3rd column divided by .5236. And,

'The 6th column is the 7th column divided 1728.

EGERTON SMITH AND CO. PRINTERS, LIVERPOOL.