CONTENTS. 
I'urther Magnetic Observations in South Africa during the Years 
1913-1916. By J. 0. Beattie, D.Sc, Professor of Physics, 
South African College, Cape Town .669 
True Isogonics and IsocUnais for South Africa for the Epoch 
July 1, 1913. By J. C. Beattie, D.Sc, Professor of Physics, 
South African College, Cape Town (Two folding Maps) . . 671 
The Heating Coefficients of Rheostats and the Calculation of Re- 
sistances for Currents of Short and Moderate Durations. By 
H. Bohle, Cape Town (Seven Text-figures) . . • .685 
Note on the So-called Vahlen Relations between the Minors of a 
Matrix. By Sir Thomas Mum ....... 695 
Descriptions of some New Aloes from the Transvaal. Part II. By 
I. B. Pole Evans (With Plates L— LVI) .... 703 
South African Perisporiales. I. Perisporiaceae. By Ethel M. 
DoiDGE, D.Sc, E.L.S., Mycologist, Union Department of 
Agriculture (With Plates LYII—LXVI) . . • . - 713 
Minutes of Proceedings of the Royal Society of South Africa , xvii 
Extracts from Reports of Recipients of Grants in Aid of Research . xxxiii 
