168 A. L. Parsons — New Sclerometer. 



Mean of first five measurements — 4'0 grm. ; mean of second 

 five measurements = 4*16 grm. ; mean of all 4*08 grin. 



Measurements with steel point (sewing needle, number 5 

 sharp) : 



E. Copper. 10 measurements : Pressure = 5*0, 4*8, 4*0, 48, 

 4*0, 4*2, 3*8, 4*2, 4*2, 4*0 grm. Mean of first five measure- 

 ments = 4*52 grm. ; mean of second five measurements = 4*08 

 grm. ; mean of all 4*3 grm. 



F. Brass. 10 measurements : Pressure = 16*4, 12*0, 10*4, 

 10-4, 9-8, 14-0, 13-0, 10-8, 10*8, 10'4 grm. Mean of first five 

 measurements = 11*8 grm. ; mean of second five measure- 

 ments = 11*8 grm. ; mean of all 11*8 grm. 



The ten measurements were made each time on the same 

 piece of copper, brass, etc. with the same inclination of the 

 surface and the same direction for the scratch. After each 

 scratch the plate was moved a little to one side by means of 

 the screw (1) so that the ten scratches were parallel and near 

 each other. 



The beginning of the scratch with the diamond point was 

 always sharp and easily seen and is a very distinct point. 

 With the steel needle, however, the beginning of the scratch 

 on steel was somewhat nncertain. The scratch did not have 

 a sharp beginning but was microscopic and gradually increased 

 in depth with the increase of pressure. 



In general a diamond point will probably give the best 

 results for all substances except possibly for those which are 

 extremely soft. Special study is being made to determine this 

 point. 



The nearly equal results obtained by scratching iron and 

 brass with diamond were surprising and the two were tested 

 against each other. The iron made a scratch on the brass very 

 easily and the brass made a scratch on the iron but apparently 

 with greater difficulty, but the point on the iron was, however, 

 sharper than the point on the brass. It would appear that in 

 the determination of hardness other properties such as tenacity, 

 elasticity, flexibility, etc. must be taken into consideration, and 

 it is hoped that this instrument may be of assistance in the 

 study of the relations between these properties. 



The results show a good determination when the mean of 

 five measurements is taken. 



The measurement is rapid and requires less than three 

 minutes for a measurement when the test object is in position 

 or for ten consecutive measurements less than a half hour. 



The advantages of the instrument above mentioned are 

 rapidity of observations, compactness, and cheapness. So far as 

 observations have been made up to the present time, the instru- 

 ment gives good results for polished faces of glass and metal, but 

 further study is necessary to show its availability for minerals. 



Heidelberg, Aug. 14, 1909. 



