NATURE 



[December 15, 1904 



there was placed a narrow glass tube, closed at the lower 

 <»nd and extending to about the centre of the flask. The 

 radium bromide weighing 23 7 milligrams was enclosed 

 in a small metal capsule supported by a thread, and was 

 inserted alternately in the glass tubes. The flasks, 

 .originally at atmospheric pressure, were immersed in a 

 water bath kept in a constant temperature room, and were 

 connected by a xylene tube which served as a manometer. 

 The healing effect was measured by the movement of the 

 xylene column, observed by a telescope with micrometer 

 eye-piece, and the scale was calibrated by a small heating 

 coil of approximately the same dimensions as the radium. 

 Two sets of experiments were carried out, in one of which 

 the ends of the glass tubes were inserted in lead cylinders 

 3 cm. in diameter and 3 cm. high, and in the other with 

 aluminium cylinders of e.vactly the same dimensions. 



The lead envelope absorbed more than half the 7 rays, 

 while the aluminium absorbed only a few per cent. I'lie 

 readings were found to be very steady and consistent, but 

 no appreciable difference in heating effect could be detected 

 in the two experiments. As a check, the heating coil was 

 ■employed in both experiments to calibrate the readings, the 

 means of which agreed to about i per cent. 



According to Paschen's results, the heating with the lead 

 cylinders should have been at least 50 per cent, greater 

 than with the aluminium cylinders. In our experiments 

 we could not have failed to detect a difference of 5 per cenT. 

 "\\'e conclude from this that the 7 rays do not supply more 

 than a small percentage of the total heating effect of 

 radium. E. Rutherford. 



H. T. B.ARNES. 



McGill Universit\", December 1 



Singularities of Curves. 



The compound singularities of algebraic curves offer a 

 wide field for discussion, but the naming of the simple 

 singularities has not yet been placed on an entirely satis- 

 factory footing. The latter consist of (i) point singulari- 

 ties, which are nodes and cusps ; {2) line singularities, which 

 I prefer to call bitangents and inflections. Mr. Basset calls 

 them double and stationary tangents ; but if this is done, 

 ^ymmetry requires that the point singularities should be 

 called double points and stationary points, and this is not 

 admissible, because the phrase double points (as now used) 

 includes cusps as well as nodes. If a curve has a double 

 point Mr. Basset calls it autotomic (self-cutting) ; but this 

 term is incorrect when all the double points in the curve 

 are cusps (as in the cardioid), for the curve does not then 

 cut itself. If it is really desirable to have a means of dis- 

 tinguishing curves that have nodes or cusps from those 

 that have none, they may perhaps best be described re- 

 ■spectivelv as curves with or without point singularities. 



December 8. T. B. S. 



A CHRISTMAS BIRD-BOOK.' 

 'T'HE success which attended his last children's bird- 

 ^ book has induced Mr. Kearton to cater once more 

 for the wants of young^ people interested in the anima 

 life around them, and the result is the present charm- 

 ing' little volume, illustrated, as usual, by reproductions 

 from photographs taken direct from nature by the 

 author and his brother. In the guise of a narrative 

 told by " Cock Robin " to his offspring, the author has 

 contrived to convey in his own inimitable manner a 

 vast store of information concerning bird-life, inter- 

 spersed with observations relating to other animals. 

 Although, as already said, intended primarily for 

 juvenile readers, the volume contains a certain 

 iimount of information which may be new to some ot 

 •their seniors, including those to whom natural history 

 is not an unknown study. For instance, until we 

 learnt it from Mr. Kcarton's pictures, we ourselves 

 were ignorant of the tnarked and easily recognised 

 ■difference between the foot-prints of a rabbit and those 

 of a hare, despite the number of times they have come 

 under our notice in the snow. 



""he Adventure of Cock Robin and hii Mate." By R. Kearton. 

 + 240; illustrated. (London: Cassell and Cj., Ltd., 1904. J Price 6i. 



NO. 1833, VOL. 71] 



Generally Mr. Kearton conveys his information in 



i simple language, but he is very prone to speak of a 



I bird picking up food between its two mandibles when 



' it would be " shorter, simpler, and better understood " 



j (to quote from a well known Bar story) if he said beak. 



Apparently old fables connected with animals die hard, 



for, according to the author, many young people at the 



' present day believe that a wren is a female robin, and 



that male robins lose their red breasts in summer. 



"Cock Robin." (Cassell and Co.). 



These and other old wives' legends Mr. Kearton does 

 his best to replace by accurate and interesting accounts 

 of the mysteries of bird-life. 



The best (if there can be a best where all is so 

 interesting) of the five chapters are the two on nest- 

 ing and the clamour of chicl^cs, both being illustrated 

 by a number of photographs of nests and young birds. 

 Very graphically does the author bring out the remark- 

 able difference in development at the date of hatching 

 between a young sparrow, for instance, and that of 

 a wcwdcock, and he also shows how much this differ- 

 ence depends on habit, a young skylark showing a 

 somewhat intermediate stage. Very striking are the 

 two photographs here reproduced, the one showing 

 young dunlins skulking amid their native covert, and 



Pp. 



the other the same birds removed to an uncongenial 

 environment. 



" Nature-teaching " could not be conveyed in a better 

 manner, or in one less free from affectation and 

 faddism, and we trust that the " Kearton annual " 

 will enjov the extensive patronage that it certainly 

 merits among those on the look-out for suitable 

 Christmas presents for their voung friends. 



R. L. 



