382 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



For the purpose of these experiments, tap bolts were prepared, 

 1J- inches in diameter, and 9 inches long, the bolt being set into 

 the stone to a depth of 6 inches. 



The holes in the stones were as nearly as possible 2 inches in 

 diameter by 6 inches deep, but in three of the experiments they 

 were tapered to a diameter of 2^ inches at the bottom. 



With an inferior quality of Babbitt metal, the bolt dre\\ 

 inch under a load of 10,000 Ibs., due to the metal coming to 

 a fair bearing. At 15,000 Ibs. the bolt drew ^ 4 inch out of 

 the setting, and at 16,000 Ibs. the stone split. 



With lead melted and poured round a bolt inserted in a 

 tapered hole, an extension of j. 2 i nc ^ was n ted under a load of 

 2500 Ibs., which did not increase until a load of 5000 Ibs. was 

 applied ; above 6000 and up to 13,000 Ibs. the extension was 

 y i i nc h for each 1000 Ibs. ; with a strain of 33,000 Ibs. on the 

 bolt the lead gave way. 



With a setting of lead pipe in a straight hole, an extension of 

 ^ inch was noted at 4000 Ibs., which did not increase until 

 a load of 10,000 Ibs. was reached ; beyond this, each successive 

 increment of load produced an extension; failure occurred 

 with a load of 25,000 Ibs. 



With sulphur, no yielding whatever was noted with a load of 

 10,000 Ibs. ; above this it was perceptible ; at 29,000 Ibs. it was 

 6 3 4 of an inch, and at 31,125 Ibs. the stone split; the fragments 

 of sulphur showed no signs of crushing. 



With the same material, in a tapered hole, no movement was 

 observed up to a load of 20,000 Ibs., but on leaving this load on 

 for five minutes an extension of T Jg- of an inch was noted, which, 

 however, did not increase. 1 



Holding Power of Drift-bolts in Timber. A number of experi- 

 ments carried out by Messrs. Powell and Harvey, of the 

 University of Illinois, United States, on the holding power of 

 square steel drift-bolts gave the following results : 



The bolts were 30 inches long and 1 inch square. The 

 timber used was pine. Holes ]^ inch, jg- inch, } inch, and 

 \% inch were bored as nearly as possible perpendicular to the 

 grain of the timber, and the bolts driven in for a depth of 6 

 inches. Five bolts were driven into each size of hole, and the 

 following average results obtained : 



1 Extract from paper read before the Washburu Engineers' Society, Mass., U.S. 

 Taken from Engineering, vol. liv. p. 88. 



