24 Kip — Determination of the Hardness of Minerals. 



chemical terras, and finally, no concurrence as to what force or 

 forces should be the measure of hardness or how these forces 

 should be combined.* The problem is indeed so complicated, 

 primarily by inherent conditions (chiefly the difficulty of 

 distinguishing hardness from allied physical properties) and 

 secondarily by the varying methods offered for its solution, 

 that here and there voices are heard pronouncing the problem 

 insolvable. Thus Daniell in his Principles of Physics states 

 that " hardness is a property that cannot be measured " and 

 Miers in his Mineralogy speaks of hardness as a character not 

 capable of absolute measurement (ed. 1902, p. 110). While 

 admitting, and indeed emphasizing the fact that the results 

 hitherto obtained are anything but convincing, I do not at all 

 agree with the views just quoted. The investigations that 

 have been made are not so much failures in themselves (quite 

 the contrary can be maintained of most of them) as they are 

 failures when regarded as solutions of one and the same problem. 

 Yiewing the history of these efforts in a general way, one is 

 struck by the fact that too often the investigators appear as 

 devotees of a certain method rather than as seekers for a certain 

 end, employing a given method and moulding it to their pur- 

 pose. And their effort appears too often as an attempt to refine 

 a method rather than to establish its serviceability. As in the 

 history of many mechanical inventions, one observes an advance 

 from simplicity to complexity but as yet no advance from com- 

 plexity to refined simplicity. Thus the metal needles of 

 Frankenheim, guided by the hand, make way for the weighted 

 point of Seebeck, under which the mineral is drawn by the hand. 

 Grailich and Pekarek replace the human hand with a pulley and 

 weight. Pfaff substitutes seven diamond points for one and 

 then passes over to the boring method for rapid determination 

 of a mean value. Jaggar carries the boring method to the 

 highest degree of delicacy, and one must add of complexity, yet 

 attained by adding clock-work and the microscope. Static 

 pressure tests have likewise advanced from the simple plan of 



* A good bibliography of the somewhat voluminous literature on the sub- 

 ject of mineral hardness will be found in Professor T. A. Jaggar's article — 

 A Microsclerometer, for determining the Hardness of Minerals, this Jour- 

 nal, Dec. 1897. The article by Franz there referred to (cited incorrectly by 

 Grailich and Pekarek) is to be found in Pogg. Annalen. Bd. lxxx, 37-55, 1850. 



To Professor Jaggar's list shotdd now be added : Rosiwal, Quarz als Stand- 

 ard-Material fur die Abniitzbarkeit ; Vienna, Verhandl. Geol. Reichsanst., 

 1902 (234-246). J. L. C. Schroeder van der Kolk, Over Hardheid in verband 

 met Splijtbaarheid, voornamelijk bij Mineralen ; Verhandel. der K. Akad, 

 Wet., 2 Sect., viii, No. 2, Amsterdam, 1902. Egon Muller, Uber Hartebe- 

 stimmung ; Inaug. Diss., Jena 1906. A fairly complete survey of the whole 

 field may be obtained by consulting the article by Grailich and Pekarek 

 (Sitzungsber. k. k. Akad., Vienna 1854, xiii) for the earlier period and the 

 dissertation of Egon Muller for the more important recent contributions. 



