Proceedings of the Polytechnic Association 819 

 October 8, 1868. 



Professor S. D. Tillman in the cliair ; Mr. C. E. Emery, Secretary. 



New Elevator. 



Mr. George R. Clarke's improved elevcator for buildings was exhi- 

 bited and explained. This elevator is designed to prevent loss of 

 life or injury to the person in tlie event of the breaking of the 

 draught or lifting rope. The elevator is furnished underneath its 

 platform with a rotating screw-blade, which works between studs 

 arranged in vertical series on the four corner posts of the well or 

 passage in which the elevator moves ; the screw-blade being turned 

 or rotated as the elevator is raised or lowered and serving to hold it 

 in a fixed position in case of the parting of the draught rope. 



A gentleman present described a plan of working a safety elevator 

 b}^ means of double ropes, one of which sustained the weight of the 

 elevator while the other ran slack over the pulleys, but was so 

 adjusted that in case the sustaining rope should break, the elevator 

 would be held by the other, after falling but a very slight distance. 

 Another member set forth a plan tried in England, in which hydrau- 

 lic pressure was employed in the operation of the elevator. The 

 platform of the latter was furnished with a downwardly extending 

 vertical tube which, through a suitable stufting-box, passed into a 

 larger tube fixed in a deep well formed in the ground, and into 

 which the water was forced by suitable means to raise the elevator. 

 This plan, although working with great smoothness and efiiciency, 

 ■was objectionable on account of its cost. 



Mr. C. E. Emery remarked that the revolving screw which works 

 by a rack, is also very safe, but has more friction than others. Then 

 there is one having a comm'on long screw with a short nut. Eleva- 

 tors that have springs to throw out prawls into notches are perhaps 

 the safest. But in all elevating machines the power used to work 

 them is too great. 



Mr. T. D. Stetson said it was evident that the screw principle is 

 much the safest of any now in use. The plan here shown is simply 

 a railroad car running up an inclined plane. 



Stump Extractor. 

 Another invention by Mr. George R. Clarke was also brought forward 

 in the shape of an improved stump-puller, which consisted in a 



