SCIENTIFIC SUMMARY. 
211 
events, it lias "been found necessary to abandon tlie mechanical working of 
the tunnel, and to use it as a simple footway. Whether, with its working 
expenses thus reduced to a minimum, it will repay its cost of construction, 
time will show. The traffic under the new arrangement has been con- 
siderable. 
Railway Tires . — A very interesting discussion is being carried on as to 
whether the tires of railway carriages are or are not more liable to fracture 
in cold weather than at other times. It has long been a popular belief that 
iron was rendered either more brittle or weaker by cold. But the belief 
does not rest on any very well established basis. On the whole, the balance 
of experimental evidence seems to show that iron is not reduced in tensile 
strength nor weaker to resist impact when very cold than at ordinary 
temperatures. Some recent ingenious experiments of Dr. Joule, communi- 
cated to the Manchester Philosophical Society, are in accordance with this 
view ; but engineers generally would be glad if Dr. Joule’s experiments 
could be repeated on a larger scale. Probably enough certain qualities of 
iron are more affected by temperature than other qualities, and in a matter 
of so much importance to the lives of travellers it is very desirable that 
fuller information on this point should be obtained. Dr. Fairbairn points 
to the crude process of shrinking the tires on the wheels, and thus inducing 
an initial state of tension in the tire as the primary cause of fracture, the 
objection to the shrinking- on process being that the exact amount of stress 
induced in the process is unknown, and depends on the skill and attention 
of the workmen. We do not remember to have seen it suggested, that 
there may be some difference in the rate of expansion and contraction of 
the iron of the tire and of the body of the wheel with change of tempera- 
ture, yet a difference may quite possibly exist. The iron of the tires and 
the wheel arms and nave is not of the same quality, . and probably the 
crystalline arrangement differs. If there were a greater contraction of the 
tire' than of the body of the wheel, this would explain the fact, alleged by 
railway managers, that more tires break in winter than summer, without 
requiring an assent to the supposed weakening of the iron. Or perhaps it 
may help to explain why steel tires enjoy a greater immunity from fracture 
in cold weather than iron ones. The same explanation will not hold in 
the case of rails, which also are stated to break more frequently in winter ; 
but, in their case, the greater rigidity of the supports when frozen would 
seem fairly chargeable with part at all events of the injury. 
Stability of Ships . — All those who are interested in the scientific problem 
presented in the calculation of the stability of ships should study the 
documents accompanying Mr. Childers’ minute on the loss of the Captain. 
Perhaps the clearest statement of the conditions to be attended to in 
estimating the stability of a vessel will be found in a very interesting paper 
by Mr. C. W. Merrifield, F.B.S., in the u Annual of the Royal School of 
Naval Architecture,” recently published. 
Adding Machine . — A very simple and neat machine for mechanically 
adding up long columns of figures will be found described in u Engineering ” 
for January 27. The instrument has been invented by Mr. Webb, of New 
York. 
New Marine Boiler . — A new form of water-tube boiler has been invented 
