In a discussion about Iron at the meeting of the Iron and Steel Institute, one of the speakers shewed that it was not so much quality of metal as mechanical structure that constituted good iron. He took certain railway bars and planed them, whereby he was enabled to examine their structure, and he saw that some of the rails contained much cinder, which accounted for their showing more signs of wear than others. On sifting the shavings and passing a magnet over them, all the iron could be taken out and the quantity of cinder ascertained; and not until this cinder could be thoroughly got rid of would the manufacturer be able to produce good iron. The same defect had been noticed in Swedish iron made for a special purpose; and there was reason to fear that manufacturers made more haste to send iron into the market than to produce the best quality. Fortunately, a few scientific men have introduced improvements which will in time abolish the rule of thumb that has too long prevailed. The manufacture of bricks from slag is still carried on at the Tees Iron-works, Middlesbrough, by machines constructed for the purpose. The slag, ground into sand, is mixed with lime, squeezed into moulds, and each machine turns out about ten thousand bricks a day. Being pressed, these bricks present advantages over ordinary bricks: they are uniform in size and thickness; do not break; occasion less trouble to the bricklayer and plasterer; require less mortar; and do not split when nails are driven into them, whereby carpenters are saved the work of plugging. Another important fact, which the labourers will appreciate, is that the weight of a thousand slag bricks is one ton less than the weight of a thousand red bricks; and as regards durability, we are informed that the longer they are kept the harder they become.