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IV. On a Th row-Testing Machine for Reversals of Mean Stress. 
Big Professor Osborne Reynolds, F.R.S., and J. H. Smith, M.Sc., Wh.Sc., 
Late Fellow of Victoria University , 1851 Exhibition Scholar. 
Received March. 5,—Read March 20, 1902. 
PREFACE. 
Although this research is a joint undertaking, I wish to point out that except for 
the idea and general design of the apparatus all the work in carrying out the design 
has been done by Mr. Smith, who has made all the calculations and superintended 
the execution of all the work which he has not executed himself. This undertaking 
occupied some two years, being not only novel but also approaching fundamental 
limits which, if passed, would have wrecked the undertaking. He has also made all 
the tests. Thus whatever success we have had is entirely owing to his knowledge, 
skill, and perseverance. In saying this, I do not wish to imply that I have not taken 
great interest in the work, for, on the contrary, I have watched it with interest and 
admiration, particularly the acumen he has shown in arranging his tests and 
interpreting the results, by which he has obtained evidence of two general laws 
which had not hitherto been suspected, one being that under a given range of stress 
the number of reversals before rupture diminishes as the frequency increases, and the 
second that the hard steels will not sustain more reversals with the same range of 
o 
stress than the mild steels when the frequency of the reversals is great. 
Owens College, OSBORNE REYNOLDS. 
February 19 th, 1902. 
Contents. 
Page 
Historical summary.266 
Objects of the research.267 
Method of applying the stress.268 
Complete description of the apparatus.268 
Determination of the stress. ..273 
Modes of vibration of a specimen.276 
The specimens : preparation, annealing, fixing.277 
Method of conducting the tests.279 
Preliminary tests for mild steel.281 
On the restoring effect of a period of rest.<.283 
Relation of limiting range to periodicity of reversals.285 
Summary of results.. , 292 
Conclusion. ...296 
VOL. CXCIX.-A 315, 
2 M 
19.9.02 
