CVIII. G. R. COWDERY. 
It should, however, be borne in mind that an ordinary fished 
joint gives little trouble for the first two years, therefore an 
extended trial is necessary before accepting the cast weld joint as 
possible perfection. Disadvantage may arise from the fact that 
cast iron and steel possess different co-efficients of expansion, and 
also whether the temper of the rail is not impaired by the heating, 
producing under heavy traffic a low place at the weld. 
With regard to the effect of temperature on the 990 feet of 
non-expansion track in Phillip Street, it may be stated that with 
a variation of temperature of 121 degrees the rails, if not neutra- 
lized and restrained by the surrounding road bed, would expand 
4:95”, and if held at the ends and permitted to bow in the centre 
would throw the rails 13’ 23” out of line. It is confidently anti- 
cipated no such variation of line or level will take place. 
As to.its practical application there are many precautions to be 
taken, such as not allowing the plate-laying to extend too great a 
distance beyond the paving or macadam filling, and also to allow 
for the removal of a defective rail, points, crossings, etc., which 
require constant attention. It is therefore not considered advis- 
able at present to lay in a greater length than 1,000 feet without 
providing for expansion. 
In conclusion, it may be stated that the climatic conditions of 
Sydney are very favourable for a continuous track. While there 
is a variation of temperature at Boston, U.S.A., of 106-5 degrees, 
New York 95 degrees, and Washington 99 degrees, the variation 
at Sydney is only 70-1 degrees Fahr. 
The author is indebted to Mr. Russell, Government astronomer, 
for information with regard to temperatures, and to Mr. Elwell 
for the latest information regarding electric welding. 
