STKK'IVH i N«; CAST IRON, KTC. 425 continues for about 90 seconds fur a total travel of the pointer of about one ami one-half decrees on the arc shown over the top of the pointer P. This is caused by the expansion of the metal at the moment of solidification, a quality, by the way, which sonic have disputed. After the expansion has fully recorded its influence, in lengthening the bar, the pointer P stands still [or about two minutes, after which time contraction be <rins and the pointer P starts to move back to the left. The weights at K arc- now suspended, and it will be well to emphasize the fact that they exert no influence ,,£ c .-A' T to suddenly move tin- pointer P backward t<» •/«•!'<». !MVC minutes after the contract ion commenced, the restrained bar's pointer will have moved about onr decree and the pointer on the free bar t\vo and one Inll derivesto the left of their starting points. About fifteen minutes after the bars an* poinvd the rest rained bar will have moved tin- pointer onr and onr half dr j^ivrs and the fret* bar three and om% half drojrrc;;, At t\u minutes after the pourin;.*;, tlu* rrstraiucd bar will have moved tin* pointer three tl«*j.;Trrs, and tin- free bar about live dr^n-rs, ,%ho\\ in:; in lii«' linir lire the other is free from any weight or restraint to prevent contraction, other than the restraint of the mould's sides, and this affords the most favorable arrangement to observe and record any difference which may exist in the contraction, etc., of free and restrained bars. Independent pointers are attached to these bars by means of levers and show their readings on scales behind them.