Oct. 19, 1882] 



NATURE 



597 



as to have any practical bearing on the behaviour of a secondary 

 battery. Oliver J. Lodge 



University College, Liverpool. 



On the Conservation of Solar Radiation 

 It appears to me a difficulty ari-es with regard to Dr. Siemens' 

 theory when we consider the original condition of the earth and 

 of the other planets. What, in fact, ha; become of the great 

 amount of energy which was present in the form of heat in those 

 bodies? 



Just as in the case of the sun, the rotation of the earth would 

 produce a continuous cycle current, the decrease of rotatory 

 energy being perhaps counterbalanced by shrinkage, the radiant 

 heat would become transformed into the potential energy of dis- 

 sociation, and this energy again would be given back to the 

 earth in the form of heat in another part of the circuit where the 

 elements recombine. Now it is quite impossible that the whole 

 of the heat radiated should be used in this way, for after a lapse 

 of years we should find a considerable diminution of potential, 

 or (perhaps) rotatory energy, and we therefore should be forced 

 to the conclusion that the earth became continually hotter. 

 Hence some of the radiant heat escaped must have escaped into 

 space, never to return. 



Is it then a feasible solution that more heat is radiating from 

 the sun than is necessary for the dissociation of the elements ? 

 If so, then at least we should have a satisfactory explanation of 

 its slowly-diminishing activity. G. 15. S. 



The writer of this letter is right in concluding that in accord- 

 ance with my hypothesis the earth also must throw out a stream 

 of matter equatorially into space ; and if your correspondent 

 will refer to my article in the Nineteenth Century of April 

 last, he will find that at p. 522 I speak of such a terrestrial out- 

 flow, with which I connect the phenomena of Aurora Borealis. 

 If at any period of the world's history the rotatory velocity of the 

 earth has been much greater than it is now, and its surface- 

 temperature sufficiently high to cause ignition of combustible 

 gases, it may be reasonably supposed that it had the power of 

 recuperating its heat of radiation. The amount of heat so 

 recuperated would, under all circumstances, be less than that 

 received back by combustion, and the result of gradual diminu- 

 tion of temperature would be that on a certain clay the tempera- 

 ture must have fallen below the point of ignition, from which day 

 forward no further recuperation of heat could be expected. The 

 process of cooling would then proceed at a very rapid ratio, 

 until the surface-temperature had reached another point of com- 

 parative constancy, at which the radiation into space was balanced 

 by the heat received by solar radiation, and which is our present 

 condition. C. W. Siemens 



12, Queen Anne's Gate, S.W., October 16 



The Great Comet and Schmidt's Comet 



There can be no doubt of the elongation of the nucleus of the 

 Great Comet in the direction of the axis of the tail, in which 

 direction it is three times as long as in a direction at right angles 

 thereto. 

 The place of the comet this morning, at6h. om. G.M.T., was 

 R.A. = ioh. iSm. 53 ± 5 sees. 

 P.D. = 103 3i'35"± 10". 

 A neighbouring object was carefully observed, through haze, 

 as a star of reference ; its place w as 



R.A = ioh. 1 8m. 53s. 



P.D. = 102° 30' o" 



On consulting the Catalogue, it appears there is no star in this 



place. The object observed was probably Schmidt's Comet, 



discovered on the 8th of this month, but not since heard of 



here. 



Unfortunately the above are absolute, not differential mea- 

 sures, but they have been corrected by measures of \ Draconis, 

 also observed as a star of reference ; its place is 

 R.A. = ioh. 4m. 46s. 

 P.D. = 101 46' 27". 



Wentworth Erck 

 Sherrington House, Bray, October 16 



[The nearest bright star to Mr. Erck's place is L. 20158, 67 

 mag. in Gould ; R.A. for 1882, ioh. 17m. 32s., N.P.D. 102 47'. 

 A Draconis is evidently a slip of the pen for \ Hydrae. — Ed.] 



The B.A. Unit 



I wish to call the attention of readers of Nature who are 

 interested in the experiments which have recently been made for 

 the determination of the B.A. unit of resistance, to a paper by 

 F. Kohlrausch, read before the Academy of Sciences at 

 Gottingen, September 6, 1882, " On the Measurement by Elec- 

 trical means of the mean Area of the windings of a Coil." Prof. 

 Kohlrausch has applied his method to redetermine the mean area 

 of the coils of the earth inductor used by him in his experiments 

 on the value of the B.A. unit in 1874. He finds the area of this 

 coil to be 387,200 sq. cm. ; the value used in 1874, calculated 

 from the geometrical measurements of Weber in 1853, was 

 392,800 sq. cm. In consequence the value of the B.A. unit as 

 determined from his experiments requires alteration, and, 

 making the necessary corrections, Prof. Kohlrausch obtains 



I B.A. unit = '990 x 10 9 — ', agreeing much more nearly 



sec. 

 with the values found by Rowland, Rayleigh and Schuster, and 

 myself. R. T. Glazebrook 



Trinity College, Cambridge, October 13 



The African Rivers and Meteorology 



Thinking that the following extract from a letter written 

 from the Niger Delta may be of interest to your readers, I beg 

 leave to offer it for insertion. 



" As yet there has been little water in the Niger, the rise up 

 to the present (August 29) has not been over 3 feet in the lower 

 river, and they say no rise has taken place in the upper river as 

 yet. The upper river commences at Locayo, or where the 

 Benue or Chadda joins the Niger, and continues thence on to 

 Timbucton. So far as I can foresee, there w ill he a famine in- 

 the Niger Valley this year, as there has been a complete failure 

 of the first crop from drought, and there has been no chance of 

 putting in the second crop for the same reason." 



The regimen of the waters of such great rivers as the Nile, 

 the Niger, and the Congo, both as to quantity and periods of rise 

 and fall, must be closely related to the meteorological conditions 

 of the highlands of Africa, so little known to us, so extensive, 

 and as yet so inaccessible for observation. May it not, there- 

 fore, be assumed that the comparative and continuous study ami 

 observation of those rivers as regards their volumes and periods, 

 of rise and fall, would be likely to furnish most valuable da'.i 

 for the prediction or forecast of weather in Europe. Thinking 

 so, I have suggested to my correspondent the advisability of 

 keeping a systematic record of the rise of the river Niger, and, 

 if possible, of the temperature and other conditions of the water, 

 with a view to their utilisation for meteorological purposes, anil 

 from this point of view I have thought that the above communi- 

 cation may present some interest. J. P. O'Reilly 



Royal College of Science for Ireland, Dublin, October 13 



A "Natural" Experiment in Complementary Colours 

 Yesterday evening I was reading Goethe's account of his 

 visit to the falls of Schaffhausen ("Journey to Switzerland in 

 1797"). After mentioning that the morning was a misty one, 

 and describing the general effect of the cataract, he adds : 

 " Wenn die stromenden Stellen griin aussehen, so erscheint der- 

 nachste Gischt lei-e purpur gefarbt." I had certainly never- 

 heard of this phenomenon before, but it naturally occurred 10 

 me that it was probably an effect of complementary colours. 

 Less than two hours afterwards I opened Nature for the week, 

 and found precisely the same phenomenon, with the same ex- 

 planation as given by Mr. C. T. Whitmell. The point is 

 interesting, as giving testimony to Goethe's close and accurate 

 observation of colour phenomena; while the coincidence involved 

 seems also to be worth recording. Walter R. Browne 



October 13 



Ventilation of Small Houses 



I HAVE been much interested in the reports of the Sanitary 

 Institute. May I call attention 10 the fact that the majority of 

 the smaller houses in our large towns have no means of ventila- 

 tion except through the rooms. There are no ventilators or 

 staircase windows, and the back house door opens into the 

 kitchen. In a three-storied house the staircase is Jit by the fan- 

 light over the front door and a skylight in the roof, neither of 



