274 Transactions of the Society. 



with rouged parchment for fine polishing. He has given, in his 

 book upon the mierostructure of metals, detailed instructions for 

 the polishing of metals and the preparation of the emery papers 

 which he found most suitable. 



Professor Arnold prepares his specimens on revolving horizontal 

 polishing blocks, and Mr. Sauveur on vertical running wheels, 

 the polishing being effected on the sides of the discs. Professor 

 H. Le Chatelier, on the other hand, polishes on the periphery of 

 vertical wheels. 



Each authority quoted has done excellent work, and it may 

 be accepted that all the devices have given satisfaction in the 

 hands of the operators. 



Professor H. Le Chatelier prepares alumina powder for the 

 polishing, and a description of the method has already been 

 furnished to this Society by Mr. W. H. Merrett. 



Messrs. Carling and Son, machinists, Middlesbrough, have for 

 many years been devoting much attention to the construction of 

 suitable devices for polishing metals by machinery, examples of 

 which are exhibited here to-night by their consent. The principle 

 of working is the same as that of other machines, such as are used 

 by Professor Ewing, Mr. W. Bosenhain, Mr. W. H. Merrett and 

 others, but there are certain improvements which are possible 

 advantages, and which have enabled me to perfectly polish a 

 specimen of steel one centimetre scjuare in about five minutes 

 after it is cut by the saw, or filed smooth. 



An examination of the accompanying photograph (fig. 56) will 

 show at a glance the construction of the machine. 



The shaft of the revolving wheel rests upon a polished steel 

 ball to prevent friction, and is caused to revolve by the cord con- 

 nected to a power-driven pulley, preferably a \ -horse power electric 

 motor, running at such a speed that the little wheel revolves at 

 the rate of between 500 and 1000 revolutions per minute. The 

 sheath S prevents the projection of the water, which is caught and 

 conveyed to the trough T. The sheath has the additional advan- 

 tage that it affords a rest for the hand when holding the specimen,, 

 and enables the operator to regulate the pressure. 



A series of loose conical blocks B are placed simply alternately 

 as required on the top of the wheel A, the friction of which is 

 sufficient to carry them round without slipping. 



The block, No. 1, is prepared by stretching a piece of the finest 

 emery cloth over its surface and securing it in position by pressing 

 the ring over the cloth and cone. The surplus cloth is removed 

 witli a knife.* 



The other blocks are prepared in precisely the same way, but 

 instead of emery cloth the paper manufactured in France for 



* These conical blocks are similar to the hand-polishing blocks designed by 

 Professor Arnold. 



