562 Intelligence and Miscellaneous Articles. 



This substance is very ductile and malleable, and its rigidity con- 

 siderable. It might be very good for use. 



(5) Alloy of Platinum 66*67 and Iridium 33*3. — Density : 

 Weight in air at 16° and 758 millims . . 53*415 grammes. 



Loss of weight in water at 16° 2*463 „ 



Density (uncorrected) 21*874 



Contraction 0*0034 



Substance not malleable. 



(6) Alloy of Platinum and Iridium 95. — Density : 



Weight in air at 16° and 744 millims. . . 51*462 grammes. 



Loss of weight in water at 13° 2*300 „ 



Density (uncorrected) 22*384 



Contraction 0*0006 



The material was reduced to fragments in the rolling-mill before 

 the determination of its density. 



It will be remarked that the above densities of platinum and 

 iridium are higher than any previously found, and that the density 

 of their alloys increases according to a very regular law — which is 

 a presumption in favour of their purity. — Comptes Rendus de VAca- 

 demie des Sciences, JNoveinber 15, 1875, foI. lxxxi. pp. 839-843. 



EXAMPLES OF CONTEMPORARY FORMATION OF IRON-PYRITES IN 

 THERMAL SPRINGS AND IN SEA-WATER. BY M. DAUBREE. 



It is known that iron-pyrites, though not usually forming large 

 masses in the crust of the earth, is extremely wide-spread, and 

 disseminated in numerous rocks, whether stratified, eruptive, or 

 metamorphic. Yet it is only rarely that at the present time this 

 mineral species is detected in course of formation. To the few 

 examples which have been certainly ascertained, I can add some 

 which will contribute to elucidate the conditions under which iron- 

 pyrites can be or may have been produced. 



Production of pyrites in the substructions at Bourhonne-les-Bains. 

 - — The iron-pyrites has not been met with at Bourbonne-les-Bains 

 among the various crystallized cupreous sulphurets deposited 

 around the Roman medals, but is produced at a little distance from 

 those incrustations, and in different parts of the subsoil. 



First, in making a sounding over the exact point of emergence of 

 the spring, there were brought up some small pebbles and grains 

 of quartz enveloped in iron pyrites. This substance is attached to 

 their surface, sometimes as an amorphous shining yellow coating, 

 and sometimes in eminently crystalline crusts in which numerous 

 triangular faces are perceptible. 



What shows clearly that its formatiou is contemporary is, that 

 it is attached, with the same characters, to some of the knife-shaped 

 flints worked by the hand of man which are found at the bottom 

 of the Roman cesspool with other antique objects. Moreover the 



