Page:Popular Science Monthly Volume 89.djvu/783

 Popular Science Monthly

��The upright G, Fig. 2, serves to carry the light-shield /, which covers the lamp-hood. It also serves partially to support the condenser-iiiouiu, which is

��Fig. 3. A slide-carrier of the conventional sort, one of the parts to be purchased

loosely placed between the slide-carrier holder and the upright G, resting upon the studs H. The dimensions of the piece G, are given in Fig. 12. The light-shield /, de- tailed in Fig. 13, is to be hard- soldered to G. Owing to the heat encountered here, a far better con- struction is to bend feet all around the cylin- der and rivet or screw it to the piece G. If solder- ing is determined larger

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the heat conducted to it is comparatively slight. The fiber-block is drilled to take the upright rod shown in the drawing and is fitted with a clamping-screw. This ad- justment will permit the lamp to be swung to either side, or raised or lowered. Theoretically, if the objective, condenser and arc are in line, no adjust- ment will be necessary, but, owing to the extreme difficulty of securing such an absolute alinement, a degree of adjust- ment is usually necessary. The holders, through which the carbons pass, are split in order that a slight friction may be exerted upon the rods.

The hood for the arc, as previously stated, consists of a small flower pot of the correct size, drilled for the holes

���2 re^. /' tjrJis rod ij'de f't in fube above

��ffiann

��Fig. 4. Plan of

front board which carries the objective

��upon, however, the ring shown in Fig. 10 may be used to strengthen the joint and to improve the appearance.

The arc-lamp illustrated in detail in Fig. 14 presents many points of interest. It is adapted for use on com- paratively small currents of from 5 to 8 amperes, and these values are practically at the topmost limit for home use. The lamp takes standard 34"''i- carbons, which are fed by merely twisting and pushing the knobs fitted to iheir ends.

Each carbon of the lamp is held in a little bracket, which, in turn, is secured to a common base of hard fiber. The use of this material is permissible in the present instance, since

��Fig. 5. Two brass rods which support the upright lens-board slide into brass tubes

��indicated, and lined by smearing it with fire-clay on the inside. When the lining is drj' and the hood fastened over the large opening in the top, the pot may be wired to the arc-lamp frame, or secured with small screws passing through the

����^\

��I reif.gjheef trass raUed info cylinder

Thii light iMfdufilaces the ujuof tn^m. Ihe ejixf lenyfh of ci/llnders /j governed tiy foa/j of lens used; air en fi'ze^ are

��Cylinder complde

��': given fiie^ for e lo W lenses.

��Seam arergd inside n/Hj/sfnj} ofdrast

��Jea/n coreradmth ^_ is/rip of ttrasj sireafe^ on

����Fig. 6. The telescoping cylinders made of thin sheet brass accurately cut and shaped with a tinner's roll

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