ECONOMICAL TUANSPORTATION. 



227 



A, is affixed a weight, which gives way at the dangerous 

 moment and returns aftei'wards to its normal position, it 



Fiii. 45. 



Support for the wire in Provin's idea. 



exerting a leverage, which is important, as the momen- 

 tum to be overcome varies with the position the support 



