302 Proceedings of Metropolitan Societies. | April, 
the effects of impact, vibratory action, and a long-continued change 
of load on wrought-iron girders was contributed to the Royal Society 
by Dr. Fairbairn. The experiments were undertaken in order to 
ascertain the extent to which a bridge or girder of wrought iron may 
be strained without injury to its ultimate powers of resistance, or the 
exact amount of load to which a bridge may be subjected without 
endangering its safety. 
To give tables of the experiments would occupy too much space, 
but we may give the results arrived at. It follows from them that 
wrought-iron girders of ordinary construction are not safe when sub- 
mitted to violent disturbances equivalent to one-third the weight that 
would break them. They, however, exhibit wonderful tenacity when 
subjected to the same treatment with one-fourth the load ; and assuming 
that an iron-girder bridge will bear with this load 12,000,000 changes 
without injury, it is clear that it would require 328 years at the rate 
of 100 changes a day before its security was affected. It would, how- 
ever, Dr. Fairbairn adds, be dangerous to risk a load of one-third the 
breaking weight upon bridges of this description, as according to the 
last experiment, the beam broke with 313,000 changes ; or a period of 
eight years, at the same rate as before would be sufficient to break it. 
But the same beam had before been submitted to 3,000,000 changes 
with one-fourth the load, and it might be that during these experi- 
ments it had undergone a gradual deterioration which must some time, 
however remote, have terminated in fracture. 
The girder experimented on, we may add, was a wrought-iron plate 
beam of the ordinary form, having a sectional top area nearly double 
that of the bottom. 
An abstract of an abstract would give a very imperfect notion of 
the ideas propounded by the Rey. Joseph Bayma ‘On Molecular 
Mechanics,” a new science, by which the author proposes to solve, 
**a problem which includes all branches of physics, and which may be 
enunciated in general terms, as follows :— 
‘From the knowledge we gain of certain properties of natural sub- 
stances by observation and experiment, to determine the intrinsic consti- 
tution of these bodies, and the laws according to which they ought to act, 
and be acted upon in any hypothesis whatever.’ There is no explaining 
a science like that of ‘ Molecular Mechanics,” as succinctly as 
Mme. De Stael once requested some German philosopher to explain 
his system—* Dites-moi votre systéme dans wn mot.” We must wait for 
the author’s volumes. 
Two short papers, one by Mr. Prestwich “On some further Evidence 
bearing on the Excavation of the Valley of the Somme by River 
Action ;” and another by the Rev. §. Haughton, “On the Joint 
System of Ireland and Cornwall,” make up the geological contributions 
to the Royal Society during the first two months of the present year. 
