UNIFICATION OF METHODS IN TESTING MATERIALS. LIII. 
In reply to Mr. Haycroft’s thoughtful discussion of the paper, 
only those points would be referred to in which he appeared to 
differ from the author. Since the paper was read, an excellent 
book on materials had reached this country written by Professor 
Johnson in which many of the points under discussion were fully 
treated. Mr. Haycroft appeared to prefer Prof. Johnson’s pro- 
portions on test pieces, and his method of locating a so-called 
elastic limit to the recommendations of the author. After care- 
fully reading Prof. Johnson’s views on these points, the author 
was unable to alter his opinion or modify it in any way for the 
following reasons. In regard to the proportions of test pieces 
pieces shewn in Figs. 1 to 6. The object of the paper as expressed 
in the title was to secure unification of the methods of testing 
materials, and the proportions given have been shown to give 
uniform results by Prof. Tetmaier and other eminent authorities, 
and have moreover been endorsed by the practise of the majority 
of the laboratories in Europe. Professor Johnson proposed pro- 
portions intermediate between those of the French and Germans, 
which have not, so far at least, been adopted by the International 
Union,— necessarily the highest authority on these matters, 
Until this was done the author saw no reason to modify these 
Proportions, as they were so simple that they could readily be 
remembered by anyone interested in the subject. 
In regard to the term Elastic Limit. A definition of this was 
given in the paper, and there can be no question that it was of 
more importance to determine this point than the yield point, but 
it was absurd to expect to locate it accurately on an ordinary 
autographic diagram. 
Professor Kennedy had succeeded in making an appliance which 
drew the stress-strain diagram for the elastic period fairly well, 
Mr. Olsen, of Philadelphia, had showed the author, about eighteen 
months ago, a very fair piece of apparatus for producing a similar 
diagram in connection with his testing machine; it was illus- 
trated on page 349 of Johnson’s book. The Grey extensometer 
apparatus on some of Mr. Richle’s machines was equally good, 
