78 



Presents. 



[Mar. 2, 



found, as in the copper wire, that there was no permanent alteration 

 unless there was permanent stretching. 



Hitherto the results on specific resistance have been given by all 

 investigators on this subject, except Lord Kelvin, in volume units, 

 but, as the alteration in density is in every case very small, the results 

 obtained in the present investigation are in very good agreement with 

 those of former experimenters. 



The conclusions arrived at are that for practical purposes any me- 

 chanical treatment, however severe, does not affect the electrical pro- 

 perties of the metals tested. As contrasted with this, it is interesting 

 to note that the smallest impurity in the metal produces a greater 

 change than the most severe mechanical treatment. For example, an 

 impurity of •§- per cent, lowers the electrical conductivity by 13*5 per 

 cent, while an impurity of f per cent, lowers it as much as 30 per 

 cent. 



III. A New Hypothesis concerning Vision." By John Berry 

 Haycraft, M.D., D.Sc. Communicated by E. A. Sohafer, 

 F.R.S. Received February 16, 1893. 



[Publication deferred.] 



Presents, March 2, 1893. 



Transactions. 



Adelaide : — Royal Society of South Australia. Transactions. 

 Yol. XV. Part 2. Vol. XVI Parti. 8vo. Adelaide 1892. 



The Society. 



Berlin :— Gesellschaft §ir Erdkunde. Zeitschrift. Band XXVII. 



No. 5. 8vo. Berlin 1892. The Society. 



Calcutta : — Asiatic Society of Bengal. Journal. Vol. LXI. 



Part 1. No. 3. 8vo. Calcutta 1892; Proceedings 1892. 



Nos. 8, 9. 8vo. Calcutta 1892. The Society. 



Charlottenburg : — Physikalisch-Technische Reichsanstalt. Vor- 



schlage zu gesetzlichen Bestimmungen iiber Electrische 



Maasseinheiten. Von Dr. E. Dorn. 8vo. Berlin 1893. 



The Institute. 



Cracow :— Academie des Sciences. Bulletin International. 1893. 



Janvier. 8vo. Cracovie 1893. The Academy. 



Essex:— Essex Field Club. The Essex Naturalist. Vol. VI. No. 12. 



8vo. Buchhurst Hill 1892. The Club. 



Kazan : — Imperial University. Scientific Notes. 1893. No. 1. 



\Russian.~\ 8vo. Kazan 1893. The University. 



