402 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



More curious, and not less useful, is the production of min- 

 eral wool above alluded to. This material, known also un- 

 der the names of slag-wool and silicate cotton, is said to be 

 made extensively at the Georg-Marien Iliitte at Osnabriick 

 and at Krupp's furnaces, in Germany, and to be largely used 

 in England as a non-conductor upon steam-pipes, boilers, etc. 

 This manufacture was made the subject of a patent in this 

 country in 1871 by Mr. John Player; and though the mate- 

 rial then produced was crude in comparison to what is now 

 produced, its non-conducting qualities gained for it a favor- 

 able report from a committee of the Franklin Institute by 

 whom it was examined in that year. Since then, however, 

 Mr. Alexander Elbers has greatly improved the process of 

 manufacture and the products; and we are assured of the 

 somewhat surprising fact that since 1876 no less than 1,000,- 

 000 pounds of the material have been made at the Clove 

 Furnace, Greenwood. 



COLD-PUNCHED vs. HOT-PRESSED NUTS. 



The method of producing nuts by a process of cold-punch- 

 ing, which was alluded to in an earlier volume of the Record 

 as a mechanical feat of extraordinary character, has achieved 

 a signal triumph during the past year, by reason of the re- 

 sults of a series of competitive tests of nuts made by this 

 and by the usual method of hot-pressing, wdiich results 

 showed most decidedly the superiority of the new process 

 over the old. 



The tests in question were made by Professor P. H. Thurs- 

 ton at the mechanical laboratory of the Stevens Institute of 

 Technology ; and w T hile we have not the space to enter into 

 the details of the experiments, it may suffice to say that the 

 tests were made both by stripping stress and bursting stress, 

 and were so elaborately and carefully conducted, upon a pro- 

 gramme mutually agreed upon by the representatives of the 

 rival systems, as to be apparently conclusive. 



The results of the trial, according to Professor Thurston, 

 may be taken as conclusive in proving : "First, that the cold- 

 punched nuts possessed a much greater average strength, 

 combined with greater rigidity, and slightly greater uni- 

 formity than were exhibited by the hot-pressed nuts ; and 

 that the superiority was most strongly manifested in the 



