310 



Popular Science Monthly 



Surveying Instrument 



The tripod and sighting in- 

 strument are constructed of 

 simple materials 



TO make a practical surveying instru- 

 ment, take a piece of tin or sheet- 

 iron two ins. wide and sixteen ins. long; 

 a piece of 7-8 in. wood shaped like a 

 triangle, three ins. on a side; three 

 strips of wood as long as the distance 

 from the ground to a little above your 

 eyes when you are standing erect; one 

 lath one foot long; and a wing-bolt. 



Bend up the strip of metal two ins. 

 from each end so as to form right angles. 

 Rcginiiing ]/i in. from the top of the bent 

 portions and extending to }4 in. of the 

 bottom, cut a slit >^ in. wide to sight 

 through. Screw or nail the metal strip 

 to the short lath. Drill a hole in the 

 middle of this apparatus to correspond 

 with the size of the wing-bolt, and one 

 in the center of the triangle. 



Now make a tripod by hinging one of 

 the three long strips to each side of the 

 triangle. Pnt a nail, with the head tiled 

 off, in the bottom of each leg to lorm 

 three anchoring points. 



F' 



To Re- Silver Old Mirrors 



iRST take off all the old silver 

 by the use of nitric acid. Rinse 

 with clear water and wipe off edges with 

 a cloth. Polish the surface of the side 

 of the glass to be silvered with rouge, so 

 as to remove grease and any foreign 

 matter. Then clean the rouged surface 

 off with a brush and a solution of chloride 

 of tin and water. 



After cleaning thoroughly rin.se with 

 clear water and lay glass on a flat table 

 that is level, being careful not to touch 

 the surface. 



Next make a solution of ^2 oz. silver 

 nitrate precipitate in ammonia with 8 

 ozs. of distilled water. Dilute yi oz. of 

 Rochelle salts in 8 ozs. of distilled water. 



After these solutions are made and the 

 glass cleaned and ready for the silver, 

 take about 8 drahms of silver solution 

 and 6 drahms of salts, mix, and pour 

 same on glass with enough distilled 

 water to flood the glass. Within three 

 hours the glass will be resilvered. 



Temporary Pole- Steps of Spikes 



THE wireless amateur interested in 

 outside aerials for his wireless 

 equipment will soon find a demand for 

 safe and substantial pole-steps on which 

 he can climb Nature's antenna poles — 

 the trees. Usually he drives in a nail at 

 some close angle. But this is very un- 

 safe, as he may loose his footing when 

 he least expects it. In the method 

 illustrated two 5-in. spikes are used in 

 making each pole- 

 step, one spike 

 being driven at a 

 horizontal line, and 

 the other directly 

 beneath it at an 

 angle of 45 degrees. 

 The one at 45 de- 

 grees is dri\en in 

 first, and then the 

 straight one. The 

 horizontal step has 

 a tendency to de- 

 press the one on 

 which it rests, and 

 results in the form- 

 er being d r i \' e n 

 Heavy splices make deeper into the 

 serviceable steps pole or tree trunk. 



