6o8 



FRANK D. ADAMS AND J. AUSTEN BANCROFT 



The objection might be put forward that, while undoubtedly 

 the tallow possesses at ordinary atmospheric pressure an internal 

 friction which is quite negligible, this material under the pressure 

 to which it must be subjected in order to deform the steel tube 

 might develop an amount of internal friction and a rigidity which 

 would be by no means negligible. 



In order to ascertain whether such was the case, companion 

 experiments were made, using the same pistons, but employing 



Fig. 4. — Longitudinal section through steel cylinder, showing the type of piston 

 used when deforming the steel with tallow. 



water in one case and oil in another, instead of tallow. It was 

 found that the deformation of the tube could be effected by either 

 of these materials, although, when water was employed, it was 

 necessary to raise the pressure rapidly at first to cause the feather 

 edges of the pistons to expand and make the joint tight, thus pre- 

 venting the water from escaping. This series of comparative experi- 

 ments was carried out with loads up to 19,000 pounds, at which 

 pressure the tubes failed, and it was found that under these pres- 

 sures the three substances mentioned — water, oil and soft tallow — 

 showed no difference in viscosity which could be detected. The 

 tallow, of course, undoubtedly possesses a somewhat greater inter- 



