502 



NATURE 



{^March 24, 1887 



The limiting distance through which it is possible to speak 

 varies inversely with the speed of the current, and that the speed 

 of the current varies inversely with the product of the total 

 resistance and the total capacity of the circuit. Hence the 

 number of reversals that it is possible to send through any 

 circuit varies inversely with the product of the total resistance 

 (R) and the total capacity (K), or the limiting distance — 



S = KR X constant (i) 



This is only another form of Thomson's law for K = Ik, and 

 R — Ir, and 



.•. S = krfi X constant. 



If the equation (i) be put into this form, 



A = irx\ (2) 



and A be given the following values : — 



Copper (overhead) i5,och3 



Cables and underground 12,000 



Iron (overhead 10,000 



the limiting distance (.r) through which speech is possible is 

 X' = A/kr. 



There is an interesting consequence of Thomson's law which 

 comes out of these experiments, and that is, whether the line be 

 a single wire completed by the earth, or a double wire making a 

 metallic circuit, the rate of speed between the two ends is 

 exactly the same, and therefore the distance we can speak 

 through is just the same whether we use a single or double wire 

 circuit. This is owing to the fact that though in the latter case 

 we double the total resistance, we halve the total capacity, and 

 therefore the product remains the same. 



The difference between copper and iron is clearly due to self- 

 induction, or to the electro-magnetic inertia of the latter, and 

 the difference between copper overground and copper under- 

 ground is due to the facility that the leakage of insulators offers 

 to the rapid discharge to earth, at innumerable points, of the 

 static charge, which in gutta-percha-covered wire can find an 

 exit only at the ends. 



It is also evident that there is no difficulty in working tele- 

 phones through underground wires, even though they attain fifty 

 miles in length, and in fact it would be better to work under- 

 ground with proper copper wire from London to Brighton, than 

 to use iron w ires along the railway telegraph poles, owing to 

 the absence of external disturbances in the former case. 



March 17. — "Second Note on the Geometrical Construction 

 of the Cell of the Honey Bee (Roy. Soc. Proc. vol. xxxix. 

 p. 253, and vol. xli. p. 442)." By Prof. H. Hennessy, F.R.S. 



The author deduces from the results established in his com- 

 munications as above cited that, while the trihedral pyramid at 

 the apex of the cell maybe inscribed in asphere whose diameter, 

 Z>, is equal to the sum of the three edges of the pyramid, another 

 sphere may be inscribed within the cell touching all of its nine 

 faces and whose diameter, /J', is equal to the diameter of the 

 cell, and that betw'een these diameters the following relation 

 exists : — 



ly \2 ' 



The connexion between the geometrical cell and its inscribed 

 and circumscribing spheres is pointed out as possibly bearing on 

 the mode cf formation of the actual cells, n 



"A Coal-dust Explosion." By W. Galloway. Communicated 

 by R. H. .^cott, M.A., F.R.S. 



Zoological Society, March i. — Prof. W. H. Flower, 

 F.R.S., President, in the chair. — Prof. Jeffrey Bell read extracts 

 from a communication sent to him by Mr. Edgar Thurston, 

 Superintendent of the Government Central Museum, Madras, 

 containing observations on two species of Batrachians of the 

 genus Cacopiis. — Mr. O. Salvin (on behalf of Mr. F. D. 

 Godman) exhibited a pair of a large and rare Butterfly 

 {Or>iithoplcya vicloricc), the male of which had been hitherto 

 undescribed. These specimens were obtained at the end of May 

 1SS6 by Mr. C. M. Woodford, at North-West Bay, Maleita 

 Island, one of the Solomon group. — Mr. E. B. Poulton read a 

 paper containing an account of his experiments on the protective 

 value of colourand markings in insects (especially in Lepido- 

 pterous larvie) in their relation to Vertebrata. It was found that 

 con.spicuous insects were nearly always refused by birds and 

 lizards, but that they were eaten in extreme hunger : hence the un- 

 pleasant taste failed as a protection under these circumstances. 



Further, conspicuous and unpalatable insects, although widely 

 separated, tended to converge in colour and pattern, being thus 

 more easily seen and remembered by their enemies. In the 

 insects protected by resembling their surroundings it was observed 

 that mere size might prevent the attacks of small enemies. 

 Some such insects were unpalatable, but could not be distinguished 

 from the others. In tracing the inedibility through the stages, 

 it was found that no inedible imago was edible in the larval 

 stage; in this stage therefore the unpleasant taste arose. — Mr. 

 G. A. Boulenger read a paper descriptive of the fishes collected 

 by the late Mr. Clarence Buckley in Ecuador. The set of all 

 the species in the collection acquired by the British Museum in 

 1880 contained a large number of highly interesting and well- 

 preserved specimens. Amongst them were representatives of 

 ten species described as new to science.— Mr. Richard S. Wray, 

 read a note on a vestigial structure in the adult Ostrich repre- 

 senting the distal phalanges of the third digit. — Mr. John H. 

 Ponsonby communicated (on behalf of Mr. Andrew Garrett) the 

 second and concluding part of a paper on the Terrestrial 

 MoUusks of the Viti or Fiji Islands. — Mr. Edgar A. Smitli gave 

 an account of a small collection of shells from the Loo-Choo 

 Islands, made by Mr. H. Pryer. 



Geological Society, February 18. — Annual General Meeting. 

 — Prof J. W. Judd, F.R.S., President, in the chair. — Having 

 presented the various medals, and the proceeds of the Donation 

 Funds in the gift of the Society, the President read his 

 Anniversaiy Address, which we have already printed. — The 

 ballot for the Council and Officers was taken, and the following 

 were duly elected for the ensuing year : — President : Prof. J. W. 

 Judd, F.R.S. Vice-Presidents: H. Bauerman, Prof. T. G. 

 Bonney, F.R.S., A. Geikie, F.R.S., Henry Woodward, 

 F.R.S. Secretaries: W. T. Blanford, F.R.S., and W. H. 

 Hudleston, F.R.S. Foreign .Secretary: Warington W. .Smyth, 

 F.R.S. Treasurer : Prof. T. Wiltshire. Council: H. Bauerman, 

 W. T. Blanford, F.R.S., Prof. T. G. Bonney, F.R.S., A. 

 Champernowne, Thomas Davies, Prof. P. M. Duncan, F.R.S., 

 A. Geikie, F.R.S., Henry Hicks, F.R.S., Rev. Edwin Hill, 

 W. II. Hudleston, F.R.S., J. W. Hulke, F.R.S., Prof. T. 

 McKenny Hughes, Prof. T. Rupert Jones, F.R.S., Prof. J. W. 

 Judd, F.R.S., R. Lydekker, J. E. Marr, E. T. Newton, Prof. 

 H. G. Seeley, F.R.S., Warington W. Smyth, F.R.S., J. J. H. 

 Teall, Prof. T. Wiltshire, Rev. H. H. Winwood, Henry 

 Woodward, F.R.S. 



February 23.— Prof. J. W. Judd, F.R.S., President, in the 

 chair. — The following communications were read: — On the 

 origin of dry chalk valleys and of Coombe rock, by Mr. Clement 

 Reid. Whilst engaged in examining the Pleistocene deposits of 

 Sussex, for the Geological Survey, the author observed that the 

 Coombe rock differs from anything commonly seen in the 

 strongly glaciated districts of the Yorkshire and Lincolnshire 

 Wolds. As in these localities, the seaward slope of the South 

 Downs is broken by the line of a partially buried sea- clift before 

 passing under the low-lying drift areas. Subsequent to the 

 formation of this sea-cliff a mass of angular flint and chalk 

 detritus spread out from the Downs over the low lands, being 

 seldom found far up the valleys. This is the Coombe rock, which 

 passes further on into a worthless mixture of angular flint and 

 loam, and at a still greater distance into almost clean brick-earth. 

 It is not of glacial origin, neither is it marine, nor is it a gravel 

 formed by ordinary fluviatile action. The rolling outline of the 

 Downs, and the steep-sided dry valleys point to conditions which 

 have passed away. However much rain may fall, the upper parts 

 of these valleys are always dry, and no running water can be 

 found where the incline of the bottom of the valley exceeds the 

 slope of the plane of saturation — never more than 60 feet per 

 mile. The author discussed the various explanations which 

 have been ofl'ered. In suggesting an origin for the dry valleys 

 and Coombe rock, he considers that the fauna and flora, both at 

 Fisherton and Bovey Tracey, point to a great degree of cold, 

 from 20° to 30° lower than what now prevails in the South of 

 England. The ground would thus be frozen to the depth of 

 several hundred feet, and the drainage system of the chalk 

 entirely modified. There would be no underground circulation. 

 The summer rains would immediately run off any steep slope, 

 often in violent torrents. These would tear up the layer of 

 rubVjle already loosened by the frost, carrying down masses of 

 unthawed chalk too rapidly for solvents to have much effect. 

 No Coombe rock is found in valleys that have a greater slope 

 than 100 feet per mile. There is no need of excessive rain- 

 fall ; it might have been a dry period corresponding to that of 



