876 EEPORT— 1887. 



The fiftli aud sixth conditions are attained hy the special peculiarity of this 

 iuveution, which consists in using thin spUt copper tubes with a quarter-inch g-ap 

 at the split. These are each six inches longer tlian one of the iron pipes. By 

 pinching the end of one of these tubes and inserting it in the end of another and 

 continuing the process, a long continuous tube can be made for carrying the bare 

 copper-wire conductors. These continuous tubes pass through the holes in the 

 insulators. The number of copper wires can be added to as the requirements of a 

 district increase. When two-thirds full these wires are all withdrawn and a bare 

 wire cable filling the whole space of the tubes is drawn through. The wires are 

 drawn through from man-hole to man-hole. A man-hole is placed at each corner 

 of a street aud serves also as a sump for pumping out accumulations of water. 

 AMien it is required to connect a house to the mains the iron pipe is drilled and 

 tapped -ndth a one-inch hole. Insulated wires are soldered to the copper tubes of 

 the required potentials, and are led to the houses through one-inch gas pipes, which 

 are screwed intt> the hole tapped in the cast-iron pipes. It will be noticed that the 

 split tubes do not act primarily as the conductors of the main current, but mainly 

 as a support for the conductors, and secondarily by contact with these as a means 

 of connection to the houses, leaving the wires free to be removed or added to. 



The seventh condition is to provide for getting round an obstacle. This is best 

 done by having hand-holes at the ends of the cast-iron pipes on each side of the 

 obstacle and joining these by lead-covered insulated cables of the full current-carry- 

 ing capacity of the system. These cables can be Ijent round the obstacle and are in 

 no way a weak point of the system. 



After describing, in these general terms, the special features of the split tube 

 system of laying underground conductors, the author proceeded to explain the 

 method of laying them in the ordinary routine. For a three-wire system and a 

 maximum of 2,000 lamps of three-quarter amperes a three-inch gas pipe may be 

 used. Each insulating disc has three one-inch holes in the positions of the angles 

 of an equilateral triangle. In adding fresh lengths of conductor three split tubes 

 are first pinched at their ends and pushed into the ends of the three split tubes 

 projecting from the last cast-iron pipe laid. Two insulators are next run along 

 the split tube to a distance from either end of the tubes of one-fourth of their length. 

 A fresh cast-iron pipe is now run along over the split tubes and their insulators, 

 the latter fitting loosely in the pipes. The joint of the pipes is made with packing 

 in the ordinary way. A new length is added in the same way. Man-holes must 

 be placed at each corner of a street, and may be half a mile apart. The cast-iron 

 pipes fit into side-holes in these boxes, and are fitted in with water-tight cement or 

 packing. Wires are pulled through from man-hole to man-hole aud may be 

 soldered together across the man-hole. Finally holes are drilled and tapped in the 

 cast-iron pipes beside those houses which require a supply of electricity. Two 

 insulated wires, bared and flattened at their ends, ai-e soldered to those split 

 copper tubes which are of the right potentials, a one-inch gas pipe is screwed into 

 the hole tapped in the main pipe, and the insulated wire is thus led into the house. 



4. On an Electric Current Meter. 

 Bij Professor G. Forbes, M.A., F.E.S. L. Sf E.—See Reports, p. 564. 



5. On the Condition of Maximum Worh obtainable fro)>i a given source of 

 alternating Electromotive Force. By Gisbeet Kapp. 



A circuit having a sensible self-induction L, and resistance r, receives current 

 either from an alternate current dynamo direct or through a transformer, theE.M.F. 

 impressed ou the terminals of the circuit being supposed to vary according to a 

 simple sine function, such as e =•■ E sin (a -i- <^), where e is the E.M.F. at any moment, 

 E is its maximum value, </> is the angle of lag, and a = tirnt, n being the reciprocal 

 of the periodic time, and t the time at which the electromotive force e is taken. 

 Graphically this electromotive force can be represented by the projection of OE^E 



