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SCIENCE PROGRESS 



us to the already quoted abstract by Delesse in the Annates 

 de chimie et de physique, and misrepresents it by telling us 

 that Delesse had only been able to separate magnetite from 

 his rocks. (" Eine ahnliche Methode wandte Delesse zu 

 Bestimmung des Magnetismus von Gesteinen und Mineralien 

 an. Er konnte jedoch dadurch nur den Gehalt von Magneteisen 

 bestimmen, denn dieses war es, welches bei seinen Versuchen 

 entrahirt wurde.") 



Like Fouque, Doelter operated with magnetic fields of 

 different intensities, obtained by varying the number of the 

 Bunsen cells (2 to 8) which he used. In this way he examined 

 many minerals, and gave a list showing the amounts by weight 

 of the crushed minerals attracted to the poles of the magnet 

 from approximately 0*25 gram in each case, varying the strength 

 of the field according to the ease with which the mineral was 

 attracted. This list in some measure resembles that prepared 

 earlier by Delesse, but is much less complete. Further, for com- 

 parative purposes, Delesse's method of using a field of constant 

 intensity and a standard for comparison is decidedly preferable 

 to the method adopted by Doelter. 



Another, though perhaps less effective method of comparison 

 used by Doelter, was to operate with a field of constant 

 intensity, and to determine the maximum distance from the 

 poles at which grains of uniform size were lifted by the magnet. 

 The results thus obtained are instructive, and are as follows : 



Doelter also gives another list, as follows, in which those 

 minerals under the same number have nearly the same magnetic 

 value, starting with the most magnetic and ending with the 

 least : 



1. Magnetite. 



2. Haematite, ilmenite. 



3. Chromite, siderite, almandine. 



