36 SCIENCE PROGRESS 
represents its magnetic power, assuming that of steel to be 
100,000 : 
Magnetite . d : . 64,121 Pleonaste : ; ; eS 
Titaniferous magnetite . 48,405 Pistacite 3 : : . 49 
Ilmenite . : é . 5,704 Allanite . : : : LAT, 
Pyrrhotite . 3 . - 43718 Jasper . 2 ; ; a 8 
Hematite . ‘ ; a 2,352 Biotite . : ; E 20) 
Hypersthene. 5 :. , 687 Idocrase. 4 : of EG 
Augite : : i) ) 3559 Axinite . 5 3 , So EF, 
Garnet (nyacineh) : . aod Sahlite . : : : Peg 
Olivine. 2 <p 250 Kyanite . : ; 5 it 22 
Hornblende : : a0 (237 Talc : ; : : as 3 
Chromite . g : x1) 7130 Aventurine . : ; ae 
Siderite  . : : Hy E20 Andesine : 2 oi, Pay 
Piedmontite : ; A 80 Tourmaline (black) : aE 
Staurolite . : : : vi) Oligoclase (sunstone) . ae! 
The above list is a very incomplete representation of Delesse’s 
results. In many cases he compared the different varieties of 
a mineral, and the results exhibited considerable variation due 
to differences in composition and the amount of impurity. For 
this reason, the numbers given in the above list cannot be 
regarded as being exact in their significance, especially when 
they are considered apart from the composition and physical 
condition of the minerals concerned ; but they serve to illustrate, 
in a general way, the variable magnetic permeability among 
minerals. 
Delesse exercised caution in making his comparative 
measurements, and avoided errors due to variation in current, 
etc. The inconstancy of the current generated by his battery 
led him to suggest that it was preferable to use a strong 
permanent magnet in making observations on the comparative 
magnetic powers of minerals. He pointed out that a compound 
horseshoe magnet was quite powerful enough for the purpose, 
while it had also the great advantage of being constant. 
His comments on the peculiarities exhibited by the different 
groups of minerals are very interesting. These comments were 
based largely on the view that the chemical constituents of 
a mineral asserted their separate magnetic effects, even in a 
state of combination. Thus he observed that the presence of 
iron, manganese, cerium, and other paramagnetic elements tends 
to increase the magnetic power of a mineral, while the presence 
of silica, alumina, lime, water, fluorine, and other diamagnetic 
constituents tends to diminish it. A broad survey of minerals 
