524 SPEEDY ELEVATOR. 



weight of the load is eflential, as it muft be multiplied by 

 the whole number of piers ; imparts the fame moment to 

 its own pier of Cvjmpetent bulk ; and in conjundtion with 

 it thickens with continual incrrafe all the others. On the 

 other hand the firmnels of piers mcreafes greatly with the 

 dccreafe of their height within certain limits. Some fpecies 

 of v\ ood have alfo correfponding degrees of ftrength. The 

 co-operation of thefe advantages may theretore render a 

 confiderable number of fhort piers light, and proportion- 

 ally fo in their refpedlive multiple moments. The more 

 numerous the piers are, the fooner is the machine wound 

 up, and let down, which is an advantage, fo far as men 

 can make greater exertions tor a fliort time. 



I) 



The form of the windlafs determines, in combination, 

 with tlie preceding, the fpeed of operation, and the degree 

 of power. It admits various modes: for example, one 

 might be placed on either fide of the pillars, with long 

 handles on the winches ; by which eight men can work 

 together. 1 his model is intended to Ihow confiJerable 

 effcds from an eafy apparatus : accordingly two men lift 

 another, and three tiers of piers : they are aided by a fuf- 

 ficient projection of the winches beyond the femiJiameter 

 of the boxes : this has fuch proportion to the height of 

 the pulleys in the pillars, and the equal length of the cords 

 a a below them, that the whole winding is done by a few 

 turns. The dimenfions of the piers are not fpecified, as 

 my experiments are not fufficient ; but 1 eftimate them fo, 

 that the elevation is at leaff fifty feet. The power in- 

 creafes, though the velocity decreafes by leflening the width 

 of the boxes ; and this can be done while their length can ^ 



fo correfpond, that the rounds of the cords a a have fuffi^ .« ' 



cient room, when the machine is wound up: 



Oblique 



