4^ Proceedings of the 



if its measure of ductility were to he determined by another mode 

 of forming the wire — extending it between half-round grooves — the 

 ductility of tin, or its reduction to wire by that process, would be 

 at least twenty times more easy than that of steel. 



There are many other interesting and uninvestigated qualities in 

 metals, such as twisting, flexion, &c. A tin wire may be twisted 

 twenty times round without breaking, when steel would snap before 

 one revolution. Yet the tenacity of steel must be more than fifty 

 times exceeding that of tin. 



Mr. B. exhibited some new instruments for measuring minute 

 differences in the diameters to the so^ooth of an inch ; and also for 

 determining comparative tenacity, flexion, and elasticity. 



In the Library was an engraved copy of an autograph of Oliver 

 Cromwell, the property of Mr. Frost. 



Friday, May I8th, and May2Mh. 

 These evenings were occupied with an account of the recent im- 

 provements in ship-building, by Mr. Holdsworth ; of which we 

 shall give the details in our next Number. 



Friday t June 1st. 



Mr. Turrell delivered a discourse on the methods o^ splitting, 

 cutting, and polishing the Diamond ; he also entered into a descrip- 

 tion of the application of that substance to effect many curious and 

 useful purposes in various manufactures practised in this country. 

 It was shown that, although the diamond is the hardest of all 

 known substances, yet it may be split by a steel tool, provided a 

 blow be applied ; but this requires a perfect knowledge of the 

 structure, because it will only yield to such means in certain direc- 

 tions. This circumstance prevents the workman from forming 

 facettes or planes generally, by the process of splitting ; he is 

 therefore obliged to resort to the process of abrasion, which is 

 technically called cutting. The process of cutting is effected by 

 fixing the diamond to be cut on the end of a stick, or handle, in a 

 small ball of cement, that part which is to be reduced being left to 

 project. Another diamond is also fixed in a similar manner, and 

 the two stones being rubbed against each other with considerable 

 force, they are mutually abraded, flat surfaces, or facettes, being 

 thereby produced. Other facettes are formed by shifting the 

 diamonds into fresh positions in the cement, and when a sufficient 

 number are produced they are fit for polishing. The stones, when 

 cut, are fixed for polishing by embedding them in soft solder, con- 



