370 



NA TURE 



[August 17, 189;; 



€ver, on giving it any delicate morsel he may find. This obser- 

 ■vation appeared to me to be of sufficient interest to record in 

 your columns, as the old male bird ceriainly ia this case learnt 

 how to feed the young one by observing the proceedings of the 

 parent birds. He had never reared any young ones of his own, 

 and had never had any opportunity of seeing other families 

 brought up in the aviary. E. Boscher. 



Belle Vue, Twickenham, Aug. 1893. 



Intrusive Masses of Boulderclay. 



The letter of Messrs. Graham Oilicer and Lewis Balfour 

 upon the glacial deposits of Bacchus Marsh suggests the de- 

 sirability of uttering a word of caution against the assumption 

 that baulder clay intercalated between two beds of rock is 

 necessarily of intermediate age. I have repeatedly observed in- 

 trusions of boulder clay into the triassic sandstones of Lancashire 

 and Cheshire, but never so striking an example as that described 

 by Mr. Arthur R. Dwerryhouie in the current number of the 

 Glacialiits' Magazine. In his paper and the accompanying 

 plale he shows how a series of glacial and triassic deposits 

 were displayed in a trench in such a way as to give the im- 

 pression that they were interbedded, sand-stone being bnh 

 below and above the glacial deposits. A minute examination 

 established the fact that the diift deposits had been thrust in 

 amongst the older rocks along a line of weakness due to the 

 presence of a bed of mirl. The intrusion had penetrated to a 

 distance o[ fifty yards from the outcrop of the marl-bed. 



I do not suggest that Messrs. Officer and Balfour have been 

 misled by such an appearance, but merely warn geologists in 

 general against falling into error. 



We have heard mu-h of late of floods and other catastrophes, 

 even from geologists possessing a considerable intimacy with 

 the phenomena of the British drift deposits. It would be 

 intere.-ting to learn in what way these injections of glacial 

 sludge would be explained by the advocates of deluges. 



Percy F. Kendall. 



Yorkshire College, Leeds, August 14. 



A Peculiar Discharge of Lightning. 



I SHOULD like to add to the many recent accounts of light- 

 Tiing discharges the following particulars of which I have not yet 

 seen any published account. 



On the afternoon of Wednesday, July 26, during a storm at 

 about 5.30, a blue flame was observed by some of the inhabit- 

 ants of Epping to approach and shatter the chimney of a house 

 upon the hill, occupied by Mrs. Brown and family at the time. 



An examination of the interior of the house shows the dis- 

 <;harge to have passed chiefly by the bell wires, which are fused, 

 down one corner of a room upon the upper floor, breaking the 

 back of a chest of drawers near, and setting the wall in the vicinity 

 on fire. 



On the ground-floor the discharge seems to have taken two 

 paths to earth, viz. down the corner of a front room by means of 

 some metallic damp-proof paper, and in the kitchen adjacent 

 by means of some wooden cupboards, the doors of which were 

 much broken and thrown acro?s the room. 



Mrs. Brown, who was seated in the front room, states that a 

 few seconds before the house was struck she noticed what ap- 

 peared to be a darkened space, surrounded by a crimson fringe of 

 flame in the corner (perhaps a brush discharged, and her son in 

 the kitchen at the time testifies to having seen a similar thing 

 previous to what appeared to be the bursting of the luminous 

 •mass, which occurred with a loud report, filling the house with 

 smoke, and the usual accompanying smell of ozone. The walls 

 are much damaged, and the polarity of a small compass in a 

 drawer of a sideboard nearest the path of discharge was re- 

 versed. I considered the apparent forewarning of the brush 

 discharge of sufficient interest to justify this letter. 



William Brew. 



Electric Light Department, British Museum, August 8. 



The Mean Density of the Earth. 

 In a note in your issue of .A.ngujt lo, adding to the list of 

 values for the mean density of the earth, which you gave on 

 July 27, it is stated that Jolly and Poynting obtained the value 

 5'58. This is, I believe, the value obtained by von Jolly, but 

 my final result, as published in the Philosophical Transactions 

 ifor 1891, is 5493 



NO. 1242, VOL. 48] 



In any account of recent work on this subject I think von 

 .Sterneck's expeiimenis at Pribram and Freiberg deserve notice. 

 These were made in the years 1S82-5, and were pendulum ex- 

 periments of the Harton Pit type. The method of comparing 

 the times of swing of the pendulums below and at the sur'ace 

 was, I believe, quite new, and consisted in determining the 

 coincidences with the same clock, which gave timubar.cous 

 half-second signals at the two stations by means of an electric 

 circuit. The results unfortunately tend to confirm the con- 

 clusion which had, I think, been already drawn from Airy's 

 work— that the mine method of experiment, though it may add 

 to our knowledge of the constitution of the surface strata, is 

 useless in determining the mean densiiy of the earth. 



Major von Sterneck's papers are published in the Procee lings 

 of the Miliia'-Geographisches Inititul of Vienna. 



Pensa.'n, Abergele, August 12. J. H. Povnti.sg. 



The Grouping of Stars into Constellations. 



Can you or some of your readers kindly give me an answer 

 to the following questions, or tell me where I may obtain 

 information on the subjects? 



Did the Assyrians, Egyptians, Greeks, and Persians group the 

 stars in the same manner into constellations? In cases where 

 they did so were the constellations usually named by all the 

 nations after the same ariimils? 



How were the constellations, which we call after Greek 

 heroes, named by Assyrians and Egyptians ? 



Do the diflerent races of the present day, Chinese, Poly- 

 nesians, Hindoos, Negroes, Americans, &c., each group the 

 stars in a peculiar way? 



If each race has its own plan of grouping the stars can we 

 make use of this peculiarity in ascertaining the aflinity of various 

 races and nations? M. h.. V,. 



Terriers Green, High Wycombe, August 11. 



Numerous Insects Washed up by the Sea. 



Have any of your correspondents mentioned the following 

 fact ? For the last two days, August 8 and 9, the shore at 

 Dymcburch, Ken', and for more than two miles towards Hyihe, 

 was covcreiJ with countless quantities of winged ants wished 

 to the shore by the waves. At low tide one sees three or 

 four rims, so thick that each makes a black stripe, from t'vo to 

 three inches wide, running without interruption for mon: than 

 three miles, and probably extending to a greater distance. We 

 havj had during these days winds from the north-east, very 

 light on Tuesday morning, but strong since that. 



Dymchurch, Kent, August 10. SuPlllE Kropotkin. 



A Substitute for Ampere's Swimmer. 



In Nature of July 27 Mr. Daniell gives a substitute for 

 Ampere's swimmer. In Denmark we use the following simple 

 ru!e given by Piof. Holten at least twenty years ago. I he 

 outstretched right hand is put in the current with the palm 

 turned toward the magnet and the fingers in the direction of 

 the current. Then the north-seeking pole will be moved in the 

 direction of the thumb. Ha.n'XA Adlicr. 



Copenhagen, August 3. 



A Correction. 



In my paper on " The Chatham Islands : their relation to a 

 former Southern Continent," just issued among the .Supple- 

 mentary Papers of the Royal Geographical Society, vol. iii., 

 there occurs a slip in the third and fourth lines from the foot of 

 page 9, which I should feel obliged by your kindly allowing me 

 to correct in your columns. My attention has been called to it 

 by Prof. Newton, of Cambridge. In quoting from his and Sir 

 Edward Newton's observations in the appendix to Captain 

 Oliver's voyage of Leguat, as to the "now submerged Conti- 

 nent," of which Rodriguez, Mauritius, Bourbon, and M.ada- 

 gascar are, according to them, the existing fragments, I 

 inserted the woidj "named I.emnria, by Dr. Sclater" after 

 the word "continent." These words of mine should have 

 occurred within square brackets, the absence of which was, 

 I regret, overlooked in the 1 roof "Now the old land-, 

 connexion," writes Prof. Newton, "of the Mascarer.e Islands 

 with Madag,ascar, of which we spoke as probable, is not at all 

 necessarily the same thing as 'Lemuria,' which Mr. Sclater 

 supposes to have reached soiie of the .Malayan countries." 



61, Glebe Place, Chelsea, S. W. 1Ii-:nry O. Forbes. 



