TKANSACTIOXS OF SECTION G. 761' 



"When steam is supplied to the jackets on the heads of the cyliadevs, but not to 

 those on the barrels, the heat consumption is 262 B.T.U. per horse-power pea 

 minute, giving a ratio of 



233: 262 = 1 : 1-12, 



which shows an appreciable but not a large eifect from using steam in the jackets 

 on the heads of the cylinders. 



It is to be remarked that this engine under its most favourable conditions 

 shows a very good efficiency, i.e., 0-183. This is 0736 of the efficiency of Camot's 

 cycle for the same range of temperatures, and is 0'813 of that of a non-conducting 

 engine having the same range of pressure. 



MONDAY, AUGUST 2?,. 

 The following Report and Papers were read : — 



1. Reioort on Small Screw Gauges. — See Reports, p. 426. 



2. Montreal Electric Tranuvay System. By G. C. Cunningham. 



3. The Present Tendencies of Electric Tramway Traction. 

 By J. G. W. Aldridge, A.M.Inst.C.E. 



Tramway work is at the present time, and has been for some years past, 

 characterised by au increasing use of mechanical traction systems. The reasons 

 for this are obvious and self-evident. It is, however, worth while to look into the 

 considerations that, so far as electric traction is concerned, have caused one system 

 or another to grow into favour, noting also the inherent qualities or attributes of 

 each, which must have an effect on future developments. 



The United Kingdom has practically 130 miles of electric tramway at work or 

 under construction; of this length 103| miles are operated on the trolley or over- 

 head wire system, 15| miles by means of a third rail conductor, 6 miles by means 

 of storage batteries, and only 4 miles on the underground conduit system. _ 



These proportions may be taken as fairly representative of other countries also,. 

 as far as can be ascertained. 



They seem likely to be maintained or even increased in favour of the overhead! 

 wire system, unless radical improvements can be made in the direction of a cheaply 

 built and maintained conduit method, or more durable and light accumulators for 

 placing direct upon the car. Objections to the overhead trolley wire system are 

 almost entirely aesthetic, but at the same time have such great weight and force that 

 every incentive is oflered to the genius of invention to make improvements in. 

 other directions. 



The ordinary underground conduit with open slot is most expensive to instal 

 and troublesome to maintain efficiently ; it cannot be built for less than 10,000/. or 

 12,000Z. per mile. Even its latest form (consisting practically of an underground; 

 trolley wire) must require an outlay of nearly double the cost of an overhead wire 

 sj-stem. 



Closed conduits with surface contacts usually operated by means of electro- 

 magnetic switching devices in boxes under the street level are complicated, and it 

 is to be feared are unreliable. The great weight of lead required on each car for 

 accumulator traction means practically that the live paying load can never reach 

 2") per cent, of the gross weight of loaded car ; whilst the combinations of trolley 

 wire and battery, attempted on systems like those of Hanover and Dresden, are 

 obviously ill-designed, the dead weight of battery being carried throughout the- 

 entire journey, though it is only required for part thereof. 



