JQ2 llev. Mr Adamson on the extent iff our 
from other causes, the required increase of resistance, only in 
those situations where it is necessary. Mr Wood * determines, 
from experiment, the relative resistance on the plate-rail and the 
edge-rail to be as 73 : 63 ; and if, as is probable, the rails in 
those experiments were swept clean, this proportion must be 
more in favour of the plate-rail than that likely to be afforded 
by the average performance upon them ; for the greatest disad- 
vantage of the plate-rail is, that it is so much more apt to retain 
upon it those substances which -increase the resistance. The 
suggestion of Mr Tredgold -j*, that the angle formed by the 
plate and its ledge should be rounded off, will, I have no doubt, 
be found advantageous in practice, as it must tend to prevent the 
rubbing of the wheels upon the ledge. 
The conclusion seems well established, that the edge-rail 
affords the most advantageous result, from the power em- 
ployed upon it ; but we still want, to a certain degree, the 
means of deciding on the comparative merits of the substances 
of which it is formed. I do not know that experiments on a 
great scale have as yet been made on any rail-roads, except 
those of cast-iron ; so that the effect of diminishing the num- 
ber of joinings, by using the longer bars of the malleable 
rails, is not exactly ascertained. But no one who has been 
dragged over both of them, or has inspected them together, 
can fail to give the malleable rails a decided preference. Of 
their comparative durability we must speak with more diffi- 
dence, until the facts be ascertained by experience ; but I do not 
imagine that there will be found ultimately much difference in 
this respect. I had an opportunity of handling part of a bar, 
referred to in a discussion on this subject in the Newcastle Cou- 
rant about a year ago. It had been in use as part of a rail-road 
about sixteen years, and except that the edges of the upper sur- 
face were considerably rounded off by the action of the wheels, 
it exhibited wonderfully slight appearances of decay. The Bed- 
lington patent rails are merely a copy in malleable iron, as close- 
* A practical Treatise on Rail-roads, See. by Nicholas Wood, 
-*•]• A practical Treatise on Rail-roads and Carriages, by Thomas Tredgold. 
When the names of those gentlemen are quoted, the above are the works re. 
i'erred to. 
