2^0 CLEA-N&ING FEATURES. 



sigmned your intention of giving in a futufe ntimber, sohf« 

 ideas upon certain singular properties of tempered steel. A 

 number of unexplained facts have for some time been known 

 to the workers of steel-plate. As I am coHcerned in a manu- 

 factory of the kind, and in the daily habit of witnessing those 

 curious and anomalous appearances, I thought you might in 

 some measure profit by the following description of .the changes 

 tvhieh take place in the various proceBses of hardening^ tem- 

 pering, hammering, burnishing, &c. 



Steel-plate har- I took a steel plate 30 inches long, 12 broad, and about 



dened and ^04. thick ; I hardened it in a composition of oil and tallow, 



then reduced ■> r 1 1 • i 



to sprins tem- ^"^d atterwards tempered it down to a spnng temper ; it was 



per, lost its ^ovv so elastic as to recover its position after being bended ; by 



hammerhio-f hammering it to set it straight, it lost a part of its elasticity ; 



grinding, &c. after being ground in the same manner as a saw, the elasticity 



became still less, having nearly returned to the same state as 



before hardened ; it was then very uniformly heated 'till it be- 



— but recover- Came blue, it now recovered the whole of its elasticity ; after 



cd the ^^'hole jj^Jng glazed bright upon a glazier coated with emery, the elas- 



jng. ticity was found to be impaired, but in a less degree than when 



it was ground ; the same effect was also produced by rubbing 



•with emery or sand-paper, and also by burnishing ; invariably 



the elasticity was recovered by bluing, and henc^ this is always 



the last operation in the manufactory of elastic steel-plate. 



Should you at some future opportunity favour the public with 



your opinion on this subject, and these hints have in the least 



assisted your inquiry, it will be the utmost wish of 



Your humble and obedient servant, 

 Sheffield, T. B. 



Jnne 18, ISO6. 



XV. 



Description of a process for clearing Feathers from their 

 AnimalOil. By Mrs. Jane Richardson.* 



T 



Fcftthei-s are JL AK]^ for every gallon of clean water, one pound of quick- 

 water*^ and""*' '"^'^ ' ^"^ ^^*^'* ^^^^^ together, and when the undissolved lim.e 

 afterwards . 



drained, wash- * For which the Society of Arts awarded twenty guineas. From 

 ed, and dried, jij^jj. Transactions, 1805, The attestations were very satifactory. 



