1850.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



91 



From the preceding table, we see that beams loaded in different degrees, bore more than beams unloaded, as below: — 



Addilloiml Load on Beam in lbs. 



Additional Load on Beam in lbs. 



Height of Fall Velocity of Impact 



necessary to answering to 



breali the Beam. that Heigiit. 



None 281 in 12682 



Lead, 41b. weight in centre.. .. 33 .... 13'301 



23 lb. in centre; no lead .. .. 42 .... 15-005 



166 lb. spread over beam + 4 lb. lead 48 .. .. 16042 



The set from the impact on these loaded beams was very great, 

 but it did not appear to injure their strengtli more than in ordi- 

 nary cases. 



389} lb. spread over beam j 4 lb. lead 

 38D II). spread over beam ; no lead.. 

 391-2 lb. spread over; 4 1b. lead 

 9o6i lb. spread over ; 4 lb. lead 



By comjiaring the imp.icts and deflections in the Abstract above, 

 it will be seen that tlie deflections are nearly as the square root of 

 the lieight fallen through by the ball, or as tlie velocity of impact. 



Abstract No. V. — Synopsis of Experiments on the Extension and Compression of Cast-Iron. 



1st. The direct Longitudinal Extension of Rod Rounds, or Bars, 50 feet long and 1 inch Area of Section nearly, of four kinds of Cast Iron, 



as mentioned below. 



In two of the bars the length, exclusive of the couplings, was 48 ft. Sin. and the extensions and sets from them have been increased 

 in the ratio of 50 to 48^25, to correspond to a length of 50 feet. 



2nd. The E.rtensions of Rods 10 feet long and 1 inch square, deduced from the preceding Experiments, and Compared with observed Compres- 

 sions of Bars of the same Irons and the same size, cast with them for comparison, together with Formulcefor computing the Weights from the 

 Extensions and Compressions. 



Extension and Compression of Cast-Iron Bars. 



The experiments to determine the effects of various weights, to 

 ext(>nd and compress bars of cast-iron longitudinally, were made 

 upon four different Ivinds of that metal. From the mean results 

 given, in the preceding abstract, of Table IX. on the extension of 



bars, and Table VI. on tlieir compression, the following formulae 

 wei-e deduced for expressing the relations between the extensions 

 and compressions of a bar 10 feet long and 1 inch square, and the 

 weights producing them respectively: — 



Extension, «j= lltillTe — 201905e= 

 Compression, w = 107763d — 3ti318d-, 



