Progress of Foreign Science. 14? 
tate the liquid from time to time. When it has become very fetid, 
the decoction of the nux vomica in water is to be poured in. This 
liquor is employedto sprinkle the objects from which insects are 
to be repelled, whether in gardens or elsewhere, taking care not 
‘to use it on gildings or polished metals, which it would blacken. 
The insect cannot stand this fetid poison. 
Art. XIV.—MISCELLANEOUS INTELLIGENCE. 
I, Mecuantcat Science. 
' 1. Remarks on Iron Wire Suspension Bridges.—The following 
remarks on this subject are from a memoire by M. Dufour, the En- 
gineer of the Geneva bridge, briefly mentioned at page 369 of the 
Jast volume of this Journal: they are naturally connected with the 
account of that bridge. 
Speaking of the comparative strength of iron in wires and in 
bars, (see p. 367 last vol.,) M. Dufour says, ‘“‘ The immense ad- 
vantage of employing iron in wire rather than in bars, is thus 
rendered evident: it is more manageable, its strength is double, 
the strength may be better proportioned by putting the number of 
wires necessary to the resistance required, and a certainty is ob- 
tained of the state of the interior parts of the suspending lines, 
which nothing can give when large bars are used.” 
“It appears at first that the minimum of the force of the wire 
should be calculated upon, and not the mean; but as each bundle 
contains many wires, although there may be some of a smaller 
strength, there will be others that will surpass in strength, and thus 
the mean should be used in estimating the strength of the whole, 
although in employing a single wire the minimum only ought to 
be taken.” 
_ With regard to the Geneva bridge, M. Dufour says that after a 
period of four months in which the bridge had been in full use, it 
ad not suffered. the slightest alteration in its primitive form, 
‘The path has retained the degree of curvature given it at first, 
and no sensible lengthening of the wires has occurred. The 
bridge, however, has been well tried, curiosity has taken great 
numbers of persons on to it at once, and all the large stones re~ 
quired in the latter part of the work, were taken over it on car 
tiages without the slightest damage. The elasticity of the bridge 
is also what it was at first, a man walking with a moderate step does 
not at all disturb the steadiness of the path; on walking quickly 
there are slight vibrations produced, but no oscillations, and the 
vibrations are such as never to be communicated from the one 
bridge to the other, or in any Hp to affect the masonry. 
2 
