. Laboratory exercises in elementary physics. Scales.—A cheap and useful form are brass hand-scales with a6-inch beam. They are sensitive to about .01 grm., and may be mounted on a five-poundstarch-box, as shown inFig. 119, the frame beingof such height that thepans hang about half aninch above the upper sur-face of the cover. Thisframe is constructed ofhard pine 2x2 in. Thescales may be suspendedfrom the cross-piece witlia screw-eye, or, if thereis a tendency to turnwhile weighing, a block ofwood, as A in Fig. 120,provided with a slot toFlG- 119- receive the top of the scale-support B, which
. Laboratory exercises in elementary physics. Scales.—A cheap and useful form are brass hand-scales with a6-inch beam. They are sensitive to about .01 grm., and may be mounted on a five-poundstarch-box, as shown inFig. 119, the frame beingof such height that thepans hang about half aninch above the upper sur-face of the cover. Thisframe is constructed ofhard pine 2x2 in. Thescales may be suspendedfrom the cross-piece witlia screw-eye, or, if thereis a tendency to turnwhile weighing, a block ofwood, as A in Fig. 120,provided with a slot toFlG- 119- receive the top of the scale-support B, which is held by the pin P, may be suspension weighing, the cover is pulled out and laid cross-wise as a support for the weight-pan, as indicated by the dottedlines in Fig. 119. A body too large for the pan may be conveniently weighedby suspension. For specific-gravity work a tumbler of liquidmay be placed as indicated by the dotted lines in the figure. Forbetter observation in this case part of the side of the box maybe CONSTRUCTION OF APPARATUS. 239 Oioss Piece. Another good form, made to order for the authors laboratory,*is shown in Fig. 62. The beam issupported upon a sharp edge by abrass post. The lower end of thepost is set into the side of astarch-box. Either form is fittedfor suspension by piercing a holethrough the centre of each the second form a half-inchhole is also bored through thewood directly below the left-handpan. This form is a little moreexpensive and more convenientthan the first. The capacity ofboth forms is from 200 to 250 grm., and their sensitiveness isnearly alike. Substitute Balances.—Balances may be constructed with awooden beam of tough wood and a wooden post attached to asuitable base-board. The pans, of tin (spice-box covers will an-swer) or stiff card-board, may be suspended by fine wire or trout-line. The beam should have some form of knife-edge device is indicated in Fig. 121. The post P is provided
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectphysics
