PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 645 



New York correspondent of 'Ihe London Technologist stated some time ago 

 that the foreman of the bindery department of the Harper Brothers, came 

 in one morning with a bar of gold, valued at $301.50, which was the pro- 

 ceeds of the gold leaf and dust swept from the floor and wiped from the 

 rags used by the binders during only three months. He further stated that 

 the gold sweepings were worth $1,500 a year, the shavings from paper 

 $5,000, shavings from pasteboard $700, and the scraps of leather $150 — 

 making an annual aggregate of $1,850, The latest 'successful utilization 

 of waste product that had come under his notice was the application made 

 by Prof. Everett, of scrap tin plate in the reduction of sulphuretted lead 

 ore. The theory of the reduction of sulphuretted lead ore by iron, is based 

 upon the fact of the great affinity of iron at a high heat for sulphur. The 

 metallic lead is set free by the sulphur leaving the ore and uniting with 

 the iron, forming the sulphide of iron. By the use of scrap tin plate the 

 iron process is carried to its highest state of perfection, because the tinned 

 iron plate is made of the very best wrought iron. Furthermore, a saving 

 is made of all the tin upon the scraps, which, for many purposes, improves 

 the quality of the lead, but it is easily separated if desired. Tin always 

 commands a far higher price than lead. Another advantage arises from 

 the thinness of these scraps, they present so much surface that part of the 

 iron is oxydized, and makes an excellent flux, thus saving the addition of 

 an artificial flux and reducing the time required for smelting very materi- 

 ally. The waste product used in this process has, until now, been thrown 

 away. In this instance the waste is more valuable than the new material, 

 At the conclusion of Dr. Parmelee's remarks, it was resolved to continue 

 the discussion of the same question at the next meeting. Adjourned. 



'■I 



American Institute Polytechnic Association, 



April 21, 1864. 



Chairman, Prof. S, D. Tillman; Secretary, Mr. B. Garvey. 



A New Pontoon Bridge. 



During the time devoted to the examination of new inventions and dis- 

 coveries, Mr. Blanchard illustrated upon the blackboard his plan for a pon- 

 toon bridge, which consists essentially in an arrangement of cylindrical 

 floats made of pine wood, in compartments, and to extend, when joined, 

 from 20 to 25 feet; they are furnished with rope handles so that they can 

 be carried by soldiers. The floats are connected by planks crossing each 

 other at their centers, each two moving on the same iron pin; each. end of 

 the plank has a similar connection with the floats by means of pins. The 

 planks are counter-braced by ropes passing through floats; by pulling on 

 these ropes the floats are thrown forward in a right line until they reach 

 the opposite bank of the river. The principle applied is that of the lazy- 

 tongs, by which the combined motion of a set of levers is made to increase 

 the motion of the last of the series. Thus a bridge may be thrown across 

 a river with great rapidity. Often it is necessary to place these bridges 

 under the enemy's fire when celerity only can insure success. The speaker 



