308 PROCEEDINGS OF SECTION B. 



No. 1 1. — Rust from fiat iron bars. 



These had been left lying on the ground exposed to the 

 weather ; the whole of the rnst was highly magnetic. 



No. 12. — Ttust from cast iron gas 'plug box. 



]4'26 grammes were passed through a No. 60 sieve, and 

 found to be wholly magnetic. 



This rust was in the form of thick scales, strongly 

 magnetic, and when broken open presented in places a 

 crystalline structure. Under the microscope some of the 

 crystals could be recognised as more or less well-formed 

 octohedrons of a bluish-black metalHc colour and lustre, and 

 they doubtless were crystals of magnetite. The scales of 

 rust were found to have in one case a sp. gr. of 4'23 at 15° C. 



No. 13. — Rust from old gate hinges. 



These had been left lying in an open barrel ; the powdered 

 rust was wholly magnetic. 



No. 14. — Rust from Sydney water mains. 



The Sydney water mains choke up very rapidly with 

 " rust," and have in consequence to be replaced from time to 

 time. The deposit consists of hydrated sesquioxide of iron, 

 iron monoxide, silica, alumina, lime, sodium chloride, kc, 

 organic matter, and some free sulphur ; the last is derived 

 from the reduction of sulphates by the organic matter. 



50 grammes of the rust from the interior of some 6-inch 

 mains, kindly supplied to me by Mr. Houghton, gave, when 

 crushed in a porcelain mortar and passed through a No. 60 

 sieve, 9*33 grammes of magnetic particles. 



50 grammes from another specimen less finely ground 

 gave 6"79 grammes of magnetic oxide. 



A third sample was passed through a No. 90 sieve, and 

 then ground in an agate mortar, but it gave much trouble 

 from clogging together into cakes. 22-719 grammes of this 

 were washed in a Knop's soil-washing apparatus. Some of 

 this was washed away and lost from its extreme lightness, 

 but the 4'02 grammes of black powder left were entirely 

 magnetic. 



No. 15. — Rust from decayed gas pipes, Melbourne. 



Mr. G. Foord, F.C.S., of the Melbourne Mint, examined 

 in 1867 certain gas pipes which had been almost wholly 



