A boiler explosion occurred in a brass foundry at Bridgeport, Ct., on the 12th inst., the force of which nearly demolished the whole building. We learn from the Farmer that the catastrophe does not appear to have been the result of carelessness on the part of the engineer, as there were no indications of a want of water, or of any undue heat in the flues, but that in the opinion of practical men it was owing to the want of sufficient strength in tho head of the boiler, which was made of cast iron, four feet in diameter, without any braces or stays for its support; it had been in use only about eight months. We cannot deprecate in too strong language the use of cast iron for heads of boilers, because it is a material totally unfitted for this purpose, owing to its friable character. Some years since, cast iron boiler heads were not uncommon in Western-made boilers, and numberless were the accidents or explosions caused by its use. It dare not be used now on any boiler subject, by law, to government inspection, and should not be allowed tj be employed in any boiler whatever.