Popular Science Monthly 



The upright G, Fig. 2, serves to carry 

 the light-shield /, whicli 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 



769 



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 



