October 25, 1894] 



NA TURE 



617 



LETTERS TO THE EDITOR. 



[Tht Editor does not hold himself responsible for opinions ex. 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of tiATXJRK. 

 No notice is taken of anonymous communications. ] 



The Inheritance of Acquired Characters. 



It may be of interest to your readers to know that two 

 guinea-pigs were born at Oxford a day oi two before the death 

 of Dr. Romanes, both of which exhibited a well-marked droop 

 of the left upper eyelid. These guinea-pigs were the offspring 

 of a male and a female guinea-pig, in both of which I had pro- 

 duced for Dr. Romanes, some months earlier, a droop of the 

 left upper eyelid by division of the left cervical sympathetic 

 nerve. 



This result is a corroboration of one series of Brown- 

 Scquard's experiments on the inheritance of acquired character- 

 istics. A very large series of such experiments are of course 

 needed to eliminate all sources of error, but this I unfortunately 

 cannot carry out at present, owing to the need of a special 

 farm in the country for the proper care and breeding of the 

 animals. Leonard Hill. 



Physiological Laboratory, University College, London, 

 October i8. 



" Rhynchodemus Terrestris " in Ireland. 



It is now nearly twenty-live years ago since Sir John Lubbock 

 discovered this Land-planarian for the first time in England. 

 .\lthough it is very doubtful whether the two other species, 

 viz. Gcodesmus bilineatiis and Bipalium kureiise, can be 

 looked upon as truly indigenous in Europe, it is not so with 

 Rhynchojeiiiiis terrestris. 



Since Midler's original discovery of this worm in 1774 in 

 Denmark, it has been taken in the Balearic Isle--, near Lille, 

 and on the Mediterranean coast in France, and near Wiirzburg 

 in Germany. Finally, Sir John Lubbock speaks of it as having 

 been found in Shropshire and Kent in England. More recently 

 Mr. Harmer discovered it near Cambridge, and I have now to 

 add a new locality, having received some specimens from Black- 

 rock, near Dublin. R. T. SCHARKi'. 



October 22. 



Dr. Watson's Proof of Boltzmann's Theorem on 

 Permanence of Distributions. 



I.v working over Dr. Watson's proof of Boltzmann's H- 

 theorem (Watson, " Kinetic Theory of Gases," second edition, 

 p. 43), it appeared that, probably through a slip, the reasoning 

 given depends or. an assumption palpably absurd, i..: that the 

 function whose vanishing defines the beginning or end -A an 

 encounter between a molecule belonging to a .set with w degrees 

 of freedom and one belonging to another set with k degrees of 

 freedom is a function of tlic coordinates of the last molecule only, 

 the one belonging to the « set. For while he lakes the number 

 of molecules of the « set whose momenta and coordinates lie 

 between 



/>, and />! -V dp^ . . . . .j,: and q„ -f dq„ 

 as 



/(/, .... ,/„)</A • ■ • ■ 'i'h.. 

 he also takes q„ = o as the condition of encounters between 

 those molecules and others from a set whose coordinates are 

 P, . . - . Q,„. 



I do not know Boltzmann's proof, but while I suppose it is 

 all right, I find it very hard to understand how any proof can 

 exist. A priori the only physical property assumed in Watson's 

 proof is that 



(//i .... dq„ = dpi ... . dq„', 



together with the fact that the number of molecules about a 

 configuration p^ . . . . q„ is 



/(/i .... q,,)dpi . . . . dq„; 



and therefore it would, if true, apply to a syslem obtained by 

 reversing the velocities when the permanent configuration had 

 been very nearly reached. Such a system would retrace its path 

 and go further and further from the permanent configuration. 

 Hence it would appear as if the whole conception of Dr. 



NO. 1304, VOL. 50] 



Watson's proof was founded on a mistaken idea of what can be 

 proved, and that all that any proof could show is that, taking 



/IT 



all the values of ' got from taking all the configurations which 



approach towards a permanent configuration of the mole- 

 cules, and the configurations which recede from the permanent 

 configuration ^obtained by reversing velocities), and then 



striking some kind of average among them, the average - 



dt 



would be negative. 



Will some one say exactly what the H-lheorem proves ? 



Edwd. p. Culverwell. 



Trinity College, Dublin, October 12. 



The Meteor-Streak of August 26, 1894. 



Since the publication of my paper in Nature of September 

 27, in which I discussed observations of the fireball of August 

 26 and its drifting-streak, I have received many additional de- 

 scriptions which show that some of the earlier reports were not 

 very accurate. The results I derived for the direction and rate 

 of motion of the sireak have therefore to be considerably 

 amended to agree with the new materials. 



From all the d.ata I find that the height of the streak was fifty- 

 four miles above a point seven miles north-east of Denbigh. 

 From thence it travelled horizontally to south-east, passing 

 successively over Ruabon, Denbighshire, and Wem and Welling- 

 ton, Shropshire, finally becoming extinct six miles west of 

 Wolverhampton, at just about the same height as at first. It 

 traversed sixty-one miles in thirty minutes, which is equivalent 

 to 176 feet per second. 



This deduction differs from the previous one, which assumed 

 the meteoric or cosmic cloud to have been rapidly ascending in 

 the atmosphere during the time it remained visible. Mr. Wood, 

 of Birmingham, obtained a similar result from the earlier 

 observations. I feel certain, however, that no such upward 

 movement of the c'oud really occurred, but that it maintained, 

 throughout its rapid drift to the south-east, a nearly uniform 

 elevation of about fifty-four miles above the earth's surface. 



Bristol, October 14. W. F. Denning. 



Flight of Oceanic Birds. 



Judging from Mr. Kingsmill's photograph, it would appear 

 that the bird is just in the position of the half-stroke of the 

 wings when making a fresh start or a sudden spurt. While these 

 birds generally sail about, yet at times they do flap their wings. 

 The movement of the wings in all these oceanic birds is very 

 deliberate. I might here be allowed to point out the interest 

 attaching to such photographs as these ; and as many have hand- 

 cameras now, snap-shots of animal life at sea, or of any natural 

 phenomena, would be valuable and interesting additions to our 

 knowledge of sea life. D. Wilson Barker. 



Greenhithe, October 13. 



A LONG-PERIOD .METEOROGRAPH. 

 TN order to obtain a record of the principal meteoro- 

 -•• logical variations at the summit of Mont Blanc, M. 

 Jules Richard, of the well-known firm of scientific instru- 

 ment makers, has constructed for Dr. Janssen a meteoro- 

 graph which will run through the winter and spring 

 without being re-wound. 



The instrument (Fig. 1) is set in action by a weight of 

 about ninety kilograms, which falls from five to six metres 

 in eight months. This weight moves a pendulum, which 

 regulates the movement of the various parts of the ap- 

 paratus. It was essential that the motion of the pendu- 

 lum should not be greatly affected by considerable 

 variations of temperature. A modified form of Denison's 

 escapement was therefore adopted by M. Richard (Fig. 

 I, A.). An advantage of this escapement is that it only 

 requires a very minute quantity of oil. Denison was un- 

 able to detect any variation in the uniform motion of the 

 pendulum when the oil had frozen to the consistency of 

 tallow. 



All the movements of the meteorograph are given to 

 the respective instruments through a horizontal shafts 



