774 



Popular Science Monthly 





A Jack to Keep Automobile 

 Weight from Tires 



A SIMPLE jack for lifting the wheels of 

 an automobile from the floor, to keep 

 the weight from the tires while it is standing 

 in the garage, is shown in the accom- 

 panying illustration. It is made of 2 by 

 5-in. material hinged together 

 with strips of i-in. stock 

 fastened to the lower block 

 The lower block should be 

 about 3 in. high and the 

 second block should be 

 long enough so that the 

 combined length of the 

 two will be about I in. 

 longer than the distance 

 from the underside of the 

 hub to the floor. The 

 method of hinging the 

 blocks together and the 

 manner of using them 

 are clearly shown. It is 

 necessary to build four of 

 these, one for each wheel.- 



8 



An individual wheel jack to keep 

 automobile weight from the tires 



-Abner B. Shaw, glass 



focusing glass to examine the image. The 

 three-legged type with adjustable glass can 

 be purchased at reasonable cost from almost 

 any dealer, and is preferable. 



Another way to do fine focusing is to get 

 fine cover glasses used in mounting speci- 

 mens for examination with a micro- 

 scope and fasten them to the ground 

 glass with Canada balsam. Since the 

 balsam has the same 

 index of refraction as 

 glass, these fine spots will 

 appear as clear glass. 

 Now place the focusing 

 glass partly over one of 

 the cover glasses and 

 focus on the surface of 

 the ground glass, paying 

 no attention to the image 

 of the object to be photo- 

 graphed. Now focus the 

 image on the screen, 

 examining it not on the 

 ground glass but in the 

 clear space of the cover 

 The image being examined is within 



ne imaqe here 



Camera Focusing Screen for Fine 

 Detail Work 



WHEN the amateur photographer is 

 confronted with the need of making 

 a picture of an object in which the detail 

 is very fine, he may find the ordinary 

 focusing methods not sufficiently exact. 

 At a slight expense, any camera with a 

 ground glass focusing arrangement can be 

 equipped with a superior focusing screen 

 equaling those employed in high-class 



p h o t o - m i - 

 crography. 



Take an 

 unexposed 

 plate having 

 a single 

 coated 

 emulsion of 

 the size used 

 in the cam- 

 era, and expose it for one second in the 

 dark room to a candle at a distance of 10 ft. 

 Developing and fixing in the usual way will 

 yield a plate with a slight tint of gray. 

 The emulsion with its exceedingly fine 

 particles of silver thrown down makes a 

 focusing screen of much finer grain than 

 the surface of the ground glass which comes 

 with the camera. The class of work which 

 calls for this kind of screen requires a 



the clear glass and is not distorted by irregu- 

 larities of surface, however small. Such 

 exact methods can yield proper results only 

 when the sensitive plate at the time of 

 exposure is in exact register with the image 

 obtained on the screen. — C. E. Drayer. 



Clear cover 



lass fastened 

 to ground qlass 

 with Canada 

 balsam 



Focusinq x qlass 



Microscopic focusing through 

 the clear places in a screen 



Lathe Centers Used as a Clamp 

 for Gluing a Box 



IN the absence of a clamp large enough to 

 hold a box I desired to glue, I used the 

 centers of my lathe as shown. The cone 

 centers were removed and a faceplate used 

 in both head and tailstock. The box was 



Box 



Wood block 



^ 



The screw of the tailstock served the purpose 

 of a carpenter's clamp for gluing the work 



placed between these parts and the tail- 

 stock screw tightened. This held the 

 parts firmly together while the glue 

 dried. It is necessary that a box have its 

 sides and ends perfectly square for gluing in 

 such a clamp, as the face-plate surfaces are 

 perfectly true and will press the parts 

 together in a straight line. — Joseph Purdy. 



