Dec. 2, 1880] 



JVA TURE 



99 



Europe, or sensibly depress the temperature of the east of North 

 America. 



Mr. Gardner makes the following hypothetical redistribution 

 of land and water ': — 



"Supposing, as all evidence tends to prove,' that Northern 

 Europe and America were connected by continuous land in 

 Eocene time, would not the mere fact of shutting off the Arctic 

 seas cause a general and perhaps sufficient rise of temperature ? " 



My answer to this is that such an arrangement of land and 

 water in the North Atlantic would raise considerably the present 

 minimum tem|)erature of the east coast of North America, but 

 would produce little or no effect in raising the already maximum 

 temperature of West Europe, which already receives the full 

 benefit of the Gulf Stream, and suffers none of the injuries of 

 the Labrador current. 



It seems to me not possible to raise the mean annual tempera- 

 ture of Bournemouth 15° F. or 20° F. without supposing an in- 

 creased Gulf Stream ; in other words, an an increased snn-keat, 

 which is contrary to the ideas of Lyell and his followers, 



I must again ask Mr. Duncan to name the species of bamboo 

 that flouri^hes so luxuriantly at Cooper's Hill under the disad- 

 vantageous conditions he has so well described 



If he decline to do so I liave no other remedy than to go to 

 the Indian Engineering College on my next visit to London, and 

 inspect and report on the bamboo myself. 



Trin. Coll. Dub., November 23 Saml. Haughton 



"Sulphuric Acid and Alkali" 

 Mr. Mactear informs me that the statements contained in 

 my review of Prof, Lunge's second volume, which appeared in 

 your columns last week, require amendment, and I beg, in 

 justice to Mr. Mactear, to make the following remarks : — 



1. It appears that the direct object of Mr. Mactear's process 

 is to reduce the amount of limestone to the least possible amount. 

 Hence the words "in excess of that usually worked "are to be 

 omitted in the sentence referring to this subject. 



2. With regard to the statement that many thousands of 

 pounds have been gained in a single works by the adoption of 

 Mr. Mactear's process, that gentleman has placed in my hands 

 the proof that this fact is correct. 



There remains however no doubt that, in the Lancashire 

 district at least, the liming process is not now so generally 

 adopted as Dr. Lunge implies ; but this may be explained by 

 the fact that Mactear's process greatly reduces the quantity of 

 caustic soda, and this does not suit the Lancashire plan of 

 working. II, E. RoscOE 



A General Theorem in Kinematics 



Prof. Minchin has been anticipated in his discovery of the 

 theorem on uniplanar motion given in Nature, vol. xxiii. p. 62. 

 It was published some six years ago by Prof. W. Schell of the 

 Polytechnikum, Carlsruhe, in the Zeilschrift fiir Mathematik 

 nnd Physik, xix. 3. The paper containing it is entitled " Ueber 

 den Beschleunigung zustand des ebenen unveranderlichcn, in der 

 Ebene beweglichen Systems," and commences at p. 1S5. The 

 two parts of the theorem will be found in leaded type at pp. igo 

 and 192. The paper (which is an admirable specimen of clear 

 writing) is purely kinematical, and treats only of motion in piano. 

 The dynamical consequences pointed out by Prof. Minchin are 

 accordingly not to be found in it ; nor the analogous theorem 

 for the general motion of a rigid body obtained by Prof. 

 Wolstenholme. The following quaternion proof of the latter 

 theorem may interest some of your readers. 



The velocity p of the particle at vector distance p from a fixed 

 origin is — p = a + K/3 p, 



a being the velocity at the origin, and fi the angtilar velocity. 



The acceleration is therefore — 



p = a-h V&f + Kj3{o + F/3p), 

 and will be zero for one definite value of p. 



Taking the point of no acceleration for origin, the constant 

 terms in the expresssion for the acceleration must vanish, and 

 the expression will be reduced to — 



p = V^p + V$ V$ p, 

 which is identical with Prof. Wolstenholme's result. 



Malone Road, Belfast, November 22 J. D. Everett 



Phosphorescent Centipedes 

 On September 28 last I was walking in my garden here at 

 eight o'clock in the evening with a friend, when we were 

 * ' I entirely deny this, but will not now turn aside from my present 

 purpose to discuss it. 



simultaneously attracted by a bright light about twenty paces in 

 front of us. The light was so bright that in the distance it 

 looked like moonlight through tlie trees ; and had the moon been 

 shinmg we should probably not again have thought about the 

 light until we came upon it. But it «as a dark nitrbt, though 

 warm and even sultry, and still. The light was so bright that, 

 taking a letter out of my pocket, I could read it. It resembled 

 an electric light, and proceeded from the bodies of two centi- 

 pedes and their two trails. The centipedes were about four 

 inches apart. The light illumined the entire body of the animal, 

 and seemed to increase its diameter three times. It flashed alono- 

 both sides of the creature in sections ; there being about six 

 sections from head to tail, between which the light played. The 

 light behaved precisely like the electric light, moving as it were 

 perpetually in two streams, one on each side, and yet lighting 

 up the whole body. In the trail there was no movement, but 

 light only. The trail extended i J foot from each centipede over 

 the grass and the gravel-walk, and it had the appearance of 

 illuminated mucus. 



Having obfervcd these creatures for several minutes, I picked 

 one of them up and lodged it in a box which had been procured 

 from the house, for further observation. On touching the 

 centipede the light in both animals, as well as in both trails, 

 was instantly extinguished. Later in the evening we found another 

 centipede, and this also emitted light in the same manner, both 

 from body and trail as I have described. My gardener then 

 informed me that he had observed these creatures during the 

 previous tliree or four evenings, both in the garden and in the 

 stableyard. 



On the following day I took the centipede to Prof. Flower, 

 who, with the assistance of the authorities of the British Museum, 

 has identified the species as Geofhilus subterranetts. 



The published descriptions of the luminous properties of the 

 British centipedes differ considerably from what I observed in 

 this instance. 



The best, so far as I know, is given in Shaw's "General 

 Zoology," vol. vi. After describing the animal, it proceeds thus : 

 "It is possessed of a high degree of phosphoric 'splendour, 

 which, however, seems to be only excited when the animal is 

 pressed or suddenly disturbed, when it diflfuses a beautiful 

 smaragdine light, so powerful as not to be obliterated by the 

 light of two candles on the same table." 



I may observe that I was never able to induce my centipede to 

 shine whilst in captivity. It may also be worthy of note that 

 the atmosphere was exceptionally dry and the barometer remark- 

 ably high at the time of the observation. 



B. E. Brodhurst 



Grange Court, Chigwell, November 22 



The Yang-tse, the_Yellow River, and the Pei-ho. 



Although the conclusions at which Dr. Woeikof has arrived 

 (Nature, vol. xxiii. p. 9) with regard to my estim.ations of the dis- 

 charge of w ater and sediment of the Vang-tse and Pei-ho may 

 militate against their being accepted as generally typical of these 

 two rivers, I would urge that another series of observations would 

 be of more service in either correcting or in corroborating my 

 estimations. 



In the case of the Yang-tse it will have been seen that, 

 according to the estimate of Capt. Elakiston at I-chang and of 

 my own at Hankow — 500,000 and 650,000 cubic feet of water 

 per second respectively, — this river increases its discharge by 

 150,000 cubic feet in the 360 miles that intei-vene between these 

 tv/o places of observation. In this portion of its course the 

 Yang-tse not only receives the waters of the Han, but is also 

 the recipient of those of the Tung-ting Lake ; and the increase 

 it receives from these two important tributaries— an amount 

 exceeding the water-discharge of the Nile' — is not such as would 

 support the conclusion that my estimate for the Yang-tSe at 

 Hankow is under the usual average. 



My observations on the Pei-ho, referring as they do to only a 

 portion of the year, are more open to correction ; and a series 

 of observations throughout the entire twelve months are certainly 

 to be pretened. 



In conclusion I may state that, although my various estimations 

 are open to criticism, my object will have been gained if, by 

 inviting further inquiry into the hydrological features of the 

 great river system of China, an accurate knowledge of them 

 is obtained. . II. B. GuppY 



' 130,000 cubic feet per second. 



