442 



Popular Science Monthly 



alternating current, an aluminum plate 

 rectifier' must be used in series with the 

 battery, together with a small lamp or other 

 suitable resistance. The aluminum plate of 

 the rectifier may consist of a small alumi- 



A type of rectifier used with the battery 

 for charging it from an alternating current 



num wire with its point just dipping into 

 the rectifier electrolyte. As the battery is 

 small, the charging current must also be 

 small. A gentle bubbling at the plates is 

 sufficient. This battery does not hold its 

 charge very long but it is a simple matter to 

 charge it each time before use, as a double 

 throw switch will change the current to the 

 charging circuit or to the apparatus 

 quickly. — R. V. Wilson. 



Wireless Signals Transmitted 

 by Telephone 



THE diagram shows how I enabled my 

 friend who had no wireless outfit to 

 listen in on my set. I installed a one-wire 

 telephone line between our homes, 



V which are about 400 ft. apart. 

 Much to my surprise this in- 

 creased the strength of the signals. 

 , mtmoNE \m 



Wiring diagram of the telephone line show- 

 ing its connection with the wireless set 



As an additional pleasure we were able to 

 talk over the telephone while wireless mes- 

 sages were coming in. — C. Wiltsee Tufts. 



An Effective Method for Recharging 

 Dry Cells 



WHAT I have found to be the most 

 effective method for recharging dry 

 cells consists in making over the construc- 

 tion^ the cell and placing it into some 

 container. Such a container may easily be 

 made from a hollow tile such as is used in 

 building construction. These tiles are cut 

 to the height of a dry cell by a hammer and 

 chisel. The tile is m „ tl _ „*,,»„. 



then stood upright 

 on"a flat board and 

 enough concrete is 

 poured in to fill the 

 bottom of the tile an 

 inch deep. After 

 the concrete has set, 

 it is coated with a 

 thin layer of melted 

 paraffin which is w 

 then allowed to cool. 

 The bottom of the 

 dry cell is then knocked off and the inside 

 compounds, with the exception of the 

 sealing compound, are then taken out. A 

 number of holes are then punched in the 

 cell, and it with its carbon is then immersed 

 in an "active" solution poured into the tile. 

 This solution is made of sal ammoniac and 

 soft or rain water in the proportion of 4 

 oz. of sal ammoniac to I qt. of water. 

 — Thomas W. Benson. 



Running Bell-Wires Through Walls 

 with an Umbrella-Rib Bodkin 



AN umbrella rib may be made to do 

 . excellent service in running electric 

 bell-wires. Such a rib is not a great deal 

 larger than the diameter of the bell-wire, 

 consequently it 

 can be run 

 through a small 

 hole. The wire 

 is stripped of its 

 covering for a 

 short distance 

 and threaded 

 through the 

 little loop near 

 the end of the 

 rib. The wire is 

 then pressed snugly into the trough of the 

 rib, which can be moved around while 

 searching for the opening without disturb- 

 ing the wire. The ball on the end of the rib 

 facilitates its easy passage through the 

 opening. — James M. Kane. 



Electric bell-wire inserted 

 with umbrella-rib bodkin 



