IRON RUST. 305 



silk some specimens set themselves in the magnetic meridian, 

 a further proof of their being magnetic and not merely 

 lumps of ordinary rust containing particles of metallic iron. 



The specific gravity v^^as found, by Joly's apparatus, to be 

 4-07 at 18°, native magnetite being 4-9 to 5*2. 



A portion of this rust yielded 70-11 per cent, metallic iron 

 (by the bichromate volumetive process), the theoretical amount 

 in magnetic oxide, Fe.^O^, being 72-41 per cent. 



To confirm or otherwise the results obtained from the old 

 rail, rust specimens were collected from various sources, and 

 these on examination verified the previous observations in 

 almost every particular. 



The rust in each case was scraped off" with a horn spatula 

 and crushed in a porcelain mortar, and the precautions 

 taken were such as to prevent any metalHc iron finding its 

 way in ; further, the magnetic powder was in every instance 

 proved to be free from any particles of iron. 



No. 2. — Rust from an old iron waggon lying on Lady 

 Robinson's Beach, near Sydney. 



The scales are about g^-inch thick, and come off" in large 

 flakes five or six inches across. On the outside, as well as the 

 inside {i.e.. next to the still unoxidised iron of the waggon), 

 they present the usual appearance of rust, being scaly 

 and of a dark-brown colour with light ochrey patches, 

 with here and there a small cone-like excrescence. Specific 

 gravity at 16° C. = 3-76. 



On breaking the scales across they present a dark — almost 

 black — coloured interior with a well marked fibrous crystal- 

 line structure, such as is seen in many Goethites. This 

 internal part gives a dark-brown streak or powder, the outer 

 film gives a pale ochre-coloured powder. The rust is picked 

 up bodily by a magnet — whether a magnetised knife-blade, a 

 horse-shoe, or electro-magnet is used — and some of the scales 

 show well marked north and south poles. On being crushed 

 it yielded a dark-brown powder, which was found to be 

 wholly lifted or attracted by a magnet, i.e., no non-magnetic 

 portion couhl be obtained from it. 



In one case 409 grammes were crushed and sent through 

 a No. 30 sieve ; only one gramme was left by the magnet, 

 and this was seen to consist of rounded grains of sand from 

 the beach. 



Another portion was crushed and sent through a No. 60 

 sieve ; this likewise was wholly attracted by the magnet. 



