STkKTrni\<; CAST rkox, KTC. 431 Aether were it not for the stretching property of cast iron. In this case, as in all else in mechanics, there is a limit to abuse, and it is not infrequent that we find this limit passed ; but when it is, the iron founder is almost invariably held responsible for the results. When the casting cracks, the designer is the last man upon whom there is any suspicion of blame, when in reality he often is the one at fault. This is not to be taken as relieving" the founder of all responsibility in the question of cracked castings, etc. When the principles involved in the stretching and contraction of cast iron are understood, he can often, by methods of cooling and permitting freedom for contraction, do much to partly relieve disproportionate castings of internal strains, which, if they do not rupture a casting before it leaves the founder's door, may often do so after it has gone into use. It must be remembered that there is hardly a piece of machinery but has some part stretched, or held in strain, and if tin; latter is the case, we may often iVar fracture or cracks, eventually cruising injury to property and loss of life.ar, it cannot but be evident that had the above wheel been left to cool olT naturally, the arms would have pulled away from the rim. This founder's achievement involves a lesson not to be forgotten by any interested in the founding or designing of machinery.