COLI.F.tTloNS IX EC'ONOMI'J (iKuLoGY AND .MKIALLlKCiV l(i3 



l\()'trts. — All of tlu' i-(liaiiH'tor Icn^tlis Imlj^tMl, tlirct* of the I'-diaiui'tor 

 (letnidiMl or fractiiroil by «>iu' portion :iii,uiilarl.\ slidiii;; oil' tlu* otiuM-, 

 whereas the others assumed a skew form without fracture. All of the 

 t-<liameters likewise chaiij^ed to a skew fbrm except the softest, which 

 Imckled in the center withonl fiactnrin^, as was also the case with all 

 of the .S<liameter8, exceptinj; one <rf the hardest, whidi snapped after 

 bneklinj;". 



Third. liouUn;/ or trtinsrersi- stress. — Strctn/fli. — The l)ars planed to 

 l.llb by l.'.tO inches jtlaced on bearinjis lit* inches apail, supported in the 

 center showed at elastic stress, 21,l.{.i, L'l,7<»(>, l.S,.J.'{;5, ir),7(>7 jiouimIs, and 

 at nltinuite stress, 32,589, 43,833, 38,145, 25,283 p<)nnds, each beinj,^ the 

 mean of the three bars tested, fjiven in the order of carbon contents. 



>Sti(}'nt:ss. — The ultimate dellection, at rupture, or that when the ^Mcat- 

 est stress was reached, was as follows: 0.78, 1.49,3.31, 5.1 1 inches, 



Effvcta. — The three bars 1.2, and the three bars 0.9, and one of the 

 O.G broke, present int; a granulated fiacluie. while the others doubled 

 up without breaking. In order to develoj) the <*,hange in the form of 

 these and of similar bars when tested some had circles drawn on their 

 sides, some diagonal lines, others transverse lines, and others both 

 transverse and longitudinal lines. 



Fourth. Ticistiiuj stress. — These si)eciinens were formed with three 

 square bosses. In testing tlie one in tiie center remains con)])aratively 

 stationary, wliilst those at eacli end are made to rotate simultaneously 

 in the same direction. 



8tre)njth. — These bars having a sectional area of 1 square inch ami a 

 torsional length of 8 diameters, resisted at elastic stress 1,135. 1,125, 

 1,08:5, 7().i pouinls, acting upon a lever 12 inches in length on each end 

 of the specimen ; and at ultimate stress 2,120, 2,336, 2,201, 1,520 pounds. 



Eigiilitij. — The amount of ultimate torsion was 0.291, 0.793, 1.021, 

 3.219, each of these being the mean of six. On examining the detailed 

 results it will be noticed that both halves of the specimen do not fracture 

 at the same time, thus B lOfiO, the first half, gave way at 0.207, whereas 

 the other half was moved to 0.227 before fracture occurred, the other 

 specimens varying more or less. 



Effects. — The lines on the three hardest bars, 1.2, show that they 

 have been twisted from two to four tenths of one turn before fracturing, 

 bars o.'.J from seven to nine tenths, 0.0, from nine tenths to otie turn 

 and one-tenth, whilst the softest from two and a half turns to three ami 

 three-qmirters previous to being fracture<l. The hardest bars all broke 

 suddenly, the fractures'being compo.sed of many spiral formed pieces 

 and all luescuting a line granular appearance. Tho.se of njcdinm hard- 

 ness all broke with a well defined spiral fracture at an angle varying 

 from 55 to57 degrees, a straight fracture between the extremities of the 

 spiral (completing the separation, presenting a tim- granular appearance. 

 The softest bars broke very dillerently to the others, as thoy all parted 

 right across, or in a |ilane i»erpeiMli(ular to the axis, presenting a 

 smooth, shining fracture. 



