670 



SCIENCE. 



[N. S. Vol. I. No. 2-1. 



not be stated that the model clears them 

 all iijj, but it shows the broader features 

 admu-ably and will be later described in 

 greater fullness. 



The speaker gave some fui-ther details of 

 the geological relations of the ore and the 

 character of the rocks as shown bj^ drill 

 cores. The presence of intruded sheets of 

 gabbro in the gneisses was especiallj' em- 

 phasized, and in particular their existence 

 as proved by the cores, immediately be- 

 neath some thin beds or veins of ore. The 

 paper was further illustrated by a large 

 series of lantern slides of the mines. 



The second paper, by G. van Ingen, on 

 ' The significance of the recent studies of 

 Mr. G. F. Matthew on Cambrian Faunas as 

 published by the Academy,' covered pv&c- 

 tically the same ground as did Mr. Mat- 

 thew's abstract printed in Science April 26, 

 p. 452. Mr. van Ingen added many ad- 

 ditional particulars based on his field ex- 

 perience in collecting the fossils, and also 

 exhibited comparative sections of the Cam- 

 brian in both Europe and America. 



The third paper, by W. D. Matthew, 

 ' The Effusive and Dike Eocks, near St. 

 John, ]Sr. B.,' was postponed on account of 

 the lateness of the hour. It appears, how- 

 ever, in full in the Transactions of the 

 Academy, and adds much to our knowledge 

 of the Pre-Cambrian volcanic rocks of JSTew 

 Brunswick. J. F. Kemp, 



Recording Secretary. 



SCIENTIFIC J0UENAL8. 



THE PHYSICAL REVIEW. 



Vol. II., No. 6. May-June, 1895. 



Tlie Capacity of Electrolytic Condensers: By 



Samuel Sheldon, H. W. Leitch and A. 



K. Shaw. 



This paper contains a description of 

 experiments performed upon two types 

 of Platinum — H2SO4 cells, which, when 

 charged to potentials less than the E. M. F. 

 of polarization, are found to act as con- 



densers. The capacity of such condensers 

 is dependent upon the impressed E. M. F. as 

 well as upon the surface and character of 

 the electrodes. Bj^ a method quite anal- 

 ogous to the ' ballistic method ' of testing 

 iron the authors have shown the presence 

 of a very considerable hysteresis in the re- 

 lation between potential and charge. The 

 curves showing this relation jjresent in fact 

 a striking resemblance to the ordinary hys- 

 teresis loop. Considerable difficulty was 

 met with in reducing the electrodes to an 

 unpolarized condition, even with new speci- 

 mens of platinum. Here also an applica- 

 tion of magnetic methods was found useful^ 

 the cells being conveniently depolarized by 

 reversals. The paper contains also an in- 

 vestigation of the effect of temperature and 

 concentration upon the capacitj'. In spite 

 of the large capacity of electrolj'tic con- 

 densers, the authors are of the opinion that 

 the high temperature coefiicient and low 

 efficiency of such cells are prohibitive tO' 

 practical usage. 



Thermal Conductivity of Cojjper, I. By E. 

 W. Quick, C. D. Child and B. S. Lan- 



PHEAR. 



In this article is begun the description of 

 observations made to determine the thermal 

 conductivity of a bar of coj^per intended for 

 use as a standard of length. The method 

 used was that of Forbes. The measure- 

 ment of the temperature at different points 

 of the bar was made bj' a method diflerent 

 from that usually employed, and depended 

 upon the variation in the resistance of a 

 coil of fine copper wire, which could be 

 shifted from point to j)oint throughout the 

 length of the bar. Eesults were obtained 

 for the conductivity through a range of 

 temperatures extending from 74° to 167°, 

 the extreme values being 0.914 at the lower 

 of these two temperatures and 1.024 at the 

 higher. Observations at temperatures- 

 below 0° will appear in a subsequent article. 



