GAUGE, Reim. An instrument for showing the depth of rain or quantity i falling on a given surface at any place. These instruments are variously con structed ; the one shown in the engraving on the following page is the inven tion of Mr. Crossley, and is an elegant application of his patent liquid metre. The principal parts of this machine, which are enclosed in a small box a a and b, are, a small tin vessel or tumbler e f, which is divided into two equal parts a vertical partition, where it is supported by pivots on the upright stem I. The pivots are placed below the centre of gravity of the tumbler, so that when it is tilted (as represented in the engraving), it will remain in that position till the upper half receives such a quantity of water as will overbalance it, when the end c will be depressed by the weight of the water, and emptied ; the end f will, in consequence, be elevated and brought under the spout to receive the water until it becomes sufficiently loaded to preponderate, when it will again take the position in the figure. Attached to this tumbler is a forked projection, that at every change of position, acts on a lever at h, and thus communi cates motion to a train of wheels, which, by the index and the dial face i, is made to register the number of times the divisions of the tumbler have been filled. The rain is received and conveyed into the tumbler by the hopper shaped vessel c c, the mouth of which must be made of an area, having such a relation to the other parts that the index will point out the number of inches ' i of rain falling on that extent of surface; or, in other words, how deep the water would have become had it remained on the surface of the earth during a single shower, a day, a month, or even a year, if required, and this, too, without any attention or care being bestowed upon it—for the apparatus is so simple in con struction, that it is not subject to derangement of its parts ; and as it registers during the falling of the shower, it requires no estimation to be made of the quantity of water evaporated between the falling of the rain and the time of observation.
GAUGING.—The art of measuring the capacities of all kinds of vessels. Gauging of course forms a part of mensuration, and is accordingly treated of by most writers on that branch of science; but as casks are seldom of any exact mathematical forms, the rules laid down by such authors must be con sidered as merely theoretical ; and in practice, gauging is performed mechani cally, by means of the gauging or diagonal rod, or by the gauging sliding rule. The diagonal or gauging rod is a rod or rule adapted for determining the con tents of the casks, by measuring the diagonal only ; viz. the diagonal from the bung to the extremity of the opposite stave next the head. It is a square rule, having four sides or faces, and is usually four feet long, and folds together by means of joints. Upon one face of the rule is a scale of inches, for taking the measure of the diagonal ; to these are adapted the areas, in gallons, of circles to the corresponding diameters. Upon the opposite face is a scale,
expressing the contents of casks, having a corresponding diagonal ; and these lines constitute the difference between the diagonal rods and the slide rules. To use the diagonal rods, put the rod in at the bung hole of the cask, until its end touch the opposite stave at the farthest possible distance from the bung hole, and note the inches and parts cut by the middle of the hung ; then draw out the rod, and look for the same inches and parts on the opposite face of it, and on them will be found the contents, in gallons. The sliding rule is similar to the common sliding Gunters, (see SCALE,) but having certain divi sors, or gauge points at different points of the scale, pointed out by small brass pins, which divisors are the number of cubic inches in any particular measure, as malt bushels, or imperial gallons, the casks are gauged approximately as cylinders, taking a mean diameter, for which purpose they are generally reduced to what is called four varieties ; and if the difference between the head and the bung diameters does not exceed six inches, their mean diameters may be found by multiplying the difference of the first by •68; of the second, by •62 ; of the third, by •55 ; and of the fourth, by •5 ; the respective products of these numbers, added to the head diameter, will make a mean diameter. Having found a mean diameter, the contents are found by setting the length of the cask upon the line marked B, on the brass slider, against the gauge point, for gallons, on the upper line A, upon the rule, and against the mean diameter upon the lower line D ; upon the rule will be found the contents on C upon the slider. On the back of the rule are four other lines, differently marked. The first line is marked D, and is similar to the same line upon the opposite side, and upon this line are set the circular gauge-point for wine, and various other gauge-points; the second line is upon the slider—it is marked C, and is similar to the same line C upon the opposite face; the third and fourth lines on this instrument are two lines of segments, for ullaging the casks, as it is termed, that is, finding the contents of a cask, only partly full. One of these lines is marked S S, for segment standing, and the other S L, for segment lying; these lines are set upon the rule, and are both numbered alike, from 1 to 10, and from 10 to 100. To find the ullage of a lying cask by the line of segments, having the bung diameter, the depth of the liquid in inches, and the contents of the cask, set the bung diameter on C to 100, on the line of seg ments marked S L, and opposite the depth of liquid on C will be a number on the line of segment, which call the reserved number ; then set 100 on A to the contents of the cask upon B, and against the reserve number before found upon A is the contents of the cask upon B. To find the ullage of a cask standing, substitute the length for the bung diameter, and the line S S, for the line S L, and proceed as before.