A. L. Parsons — New Sclerometer. 



167 



Weight 

 grm. 



Eeading 



Deflection of 



needle in 



divisions of 



graduated 



circle 



No. of 

 divisions 

 equivalent 

 to 1 grm. 



Mean No. of 



divisions 



equivalent to 



1 grm. 



Second trial. 



211-5 











5 



199-0 



12-5 



2-5 





10 



186-5 



25-0 



2-5 





20 



162-5 



49-0 



2-48 





50 



86-0 



125-5 



2-51 



2-4975 



Third trial. . 



135-0 











5 



123-0 



12-0 



2-4 





10 



110-0 



25-0 



2-5 





20 



85-0 



50-0 



2-5 





50 



70 



128-0 



2-56 



2-49 



Fourth trial. 



193-5 











5 



180-5 



13-0 



2-6 





10 



168-5 



25-0 



2-5 





20 



143-5 



50-0 



2-5 





50 ' 



67-0 



126-5 



2-53 



2-5325 



Mean of all 









.. 2-4975 



The results agree closely so that the elevation may be con- 

 sidered proportional to the weight and in this instrument a 

 load of 10 grams is equivalent to 25 divisions on the microm- 

 eter screw. 



Results of Measurements. 



Plane and polished surfaces of glass, iron, copper, and brass 

 were taken as test objects. A few trials were made with 

 crystal faces, but further study is necessary before it can be 

 stated that the instrument is suitable for determining the 

 hardness of unpolished surfaces. 



Measurements with the diamond point (a tetrahedral cleav- 

 age fragment) : 



A. Copper. 10 measurements : Pressure = 1*2, 1*2, 1*8, 

 1-6, 1-6, 1-4, 1-6, 1-8, 2-0, 1-4 grm. Mean of first five meas- 

 urements = 1*48 grm. ; mean of second five measurements =■ 

 1'44 grm. ; mean of all 1*46 grm. 



B. Brass. 10 measurements: Pressure = 1*6, 2*0, 2*2, 2'2, 

 2-0, 2-2, 2-2, 2-2, 1'6, l'T grm. Mean of first five measure- 

 ments = 2'00 grm. ; mean of second five measurements = 

 1*98 grm. ; mean of all 1*99 grm. 



C. Iron (rolled). 10 measurements : Pressure = 2*2, 1*8, 

 2-0, 1-6, 2-2, 2-0, 2-2, 1'8, 2'0, P8 grm. Mean of first five 

 measurements — 1*96 grm. ; mean of second five measurements 

 = 1*96 grm.; mean of all 1'96 grm. 



D. Glass {object glass for microscope). 10 measurements: 

 Pressure = 3'8, 4*0, 4'2, 4-0, 4'0, 3*8, 4*2, 4'2, 4-2, 4-4 grm. 



