162 A. L. Parsons — New Sclerometer. 



Art. IX. — A New Sclerometer ; by A. L. Parsons (Uni- 

 versity of Toronto). 



The physical properties of minerals and metals have for a 

 long time been a subject for investigation, and among the first 

 of these properties to be studied were hardness and tenacity, 

 but although the tensile strength and crushing point of the 

 various substances are easily measured, the determination of 

 hardness or resistance which a substance offers to abrasion is 

 not so well understood. The sclerometer which was devised 

 by Seebeck and later improved by Grailich and Peckarek is 

 the one which is best known, but it is little used because the 

 length of time which is required for a single measurement 

 prevents the common use of an instrument which should be 

 of valuable assistance to the mineralogist and metallurgist. 



A bibliography of works on sclerometry is given by Jaggar* 

 which includes the most important papers and outlines the 

 principles employed by various investigators in using their 

 own instruments or those devised by others. 



The new instrument differs from those of Seebeck, Grailich 

 and Pekarek and others in that the force that is necessary to 

 make a scratch is measured by means of a spring and not by 

 weights. 



Description of the Instrument^ 



The instrument consists of four working parts on a base, as 

 follows (see fig. 1) : — 



1. Steel spring (F) with test-point holder (JET) fastened to 

 the column (S). 



2. Object holder (O) with divided horizontal circle (C), 

 horizontal screw (1) for moving the object to be tested from 

 side to side, and two vertical screws (2 and 3) to give the object 

 the desired inclination. 



3. Carriage (7) with transport screw (4) and spring (5) to 

 move the test object, while making the scratch, and a slide (6). 



4. Micrometer screw (E) and scale (8) to measure the eleva- 

 tion, which is proportionate to the force necessary to make a 

 scratch. 



5. Base (G) to hold the working parts together. 



1. The spring (F) consists of a strip of steel 120 mm long, 

 from the column (S) to the test point, 4-8' mn wide and 0"75 mm 

 thick. It is firmly fastened by a screw to the top of the 



* This Journal (4), iv, p. 399, 1897. 



f Price of instrument, 80 marks from the mechanic, P. Stoe, Heidelberg^ 

 Germany, Jubilaeums Platz, 70. 



