Show why soldiers banks there are very few bridges in the world over which troops are allowed to march in regular step in general when coming to a bridge particularly a suspension bridge the drums or lands are stopped tho array is broken and the soldiers pass over without keeping step or rather taking pains not to keep step the reason is found in the act that a very slight initial vibration if continued is imparted to the whole structure and in a short time becomes so strong a downward strain at every recurrence as speedily to endanger the safety of the strongest bridge the same principle is illustrated in some houses which can be made to tremble from roof to foundation by persistently and regularly pressing with the foot on a loose board in one of the floors A similar curious circumstance is seen in the case of certain churches in which it is dangerous to play the pedal pipes of a grand or ganfor the reason thai the vibration becomes so great as to shatter the panes of glass in the windows and even to impell the safety of the roof st louis alobe democrat A kind or moth or buttery is said to have become so very troublesome and destructive in bavaria that every possible means has been taken to destroy it the most effective method consists of attracting the pest by means of an electric light in connection with a blow fan which draws the insects into the suction pipe by air draught and resilia in mill tons of them being destroyed |