June 15, 1876] 



NATURE 



149 



being the case with most of the Riviera torrents. For instance, 

 the channels of the streams near Menton, Vintimiglia, and else* 

 where, are far out of all proportion to the work they have to do. 

 Take the case of the principal stream at Menton. At a distance 

 of less than two miles from the sea where its bed is formed of 

 rock, it has only a breadth of a few yards, and has no high 

 flood-marks indicating that there is ever a great depth of water. 

 If the stream is followed downwards from this point for less than 

 a mile, the bed is found to open out to a breadth of from sixty 

 to seventy yards. Between these points there are no tributary 

 streams adding their waters to account for this increase. These 

 large river-beds are caused by the nature of the country which 

 these rivers drain. The country is very mountainous, the hill 

 slopes are rocky and steep, large areas have no covering of soil, 

 and what soil there is does not retain the water well. The 

 result of this is, that when rain falls the water rapidly finds its 

 way to the streams, and the same amount of rainfall is 

 discharged by these streams in a few hours as is discharged in 

 weeks by an English river draining the same area. This ac- 

 counts for these torrents rising so " high " and falling so " low." 

 It also accounts for them " rising " and " falling " rapidly. 



But further^ the great and unnecessary breadth of these torrent- 

 beds where they approach the sea seems to be produced somewhat 

 in the following way : — The valleys through which these streams 

 flow descend rapidly from the mountains, but as they approach 

 the sea their slope becomes much slower; the result of this is, that 

 the gravel brought down by the river from its higher and more 

 rapid reaches, is here deposited, on account of the water losing 

 its velocity, and the bottom of the valley becomes filled with a 

 bed of gravel, through which the stream winds sometimes in 

 one part, sometimes in another. A very small cause being suffi- 

 cient to make the stream " cut " into the gravel and alter the 

 position of its bed, and cause it to flow in different parts of the 

 channel at different times, but it almost never covers at one time 

 the whole breadth of it. 



That the bed of the principal stream at Menton is unneces- 

 sarily large, is evident from the fact that now, on account of the 

 increased value of land, they are building a retaining-wall near 

 the centre of the stream, and filling up about one-half of the 

 river-bed for the purpose of cultivation. 



Rivers similar to those of the Riviera are common to all moun • 

 tainous countries, Britain not excepted. There is at least one 

 salmon river in Scotland, which during the dry season may be 

 walked across without wetting the soles of one's boots, all the 

 water finding a passage among the gravel. Yet in Autumn, 

 when it has lallen to " fishing condiuon," it is a stream of about 

 thirty yards broad, and an average depth of about two feet on 

 the fords. This river is also subject to great floods:, which 

 " come down " rapidly, and " fall " rapidly. It also has gravel 

 deposits similar to those of the Riviera torrents, but in this case 

 they are covered with soil and cultivated, and it is with the 

 greatest difficulty and at great expense that the river is pre- 

 vented from widening its channel to the proportions of those of 

 the Riviera torrents. John Aitken 



Bellagio, Lago di Como, Italy 



t 



Method of Distributing Astronomical Predictions 



I BEG leave to observe that the very useful method of dis- 

 tributing astronomical predictions over a given geographical area 

 alluded to in Nature, vol. xiii., page 71, and ascribed there to 

 Mr. W.lS. B. Wool house, was already proposed by my father, 

 J. J. von littrow, in his treatise, " Darstellung der Sonnen- 

 finstemiss vom 7 September, 1820," Pest, 1820, 2S> well as in the 

 Berliner Astronomisches Jahrbuch, for 1821, page 1 16, and 

 1822, page 145; subsequently in his " Theoretische und prac- 

 tische Astronoroie," Wien, 1821, part ii., page 280 ; and last in 

 his " Vorlesungen iiber Astronomic," Wien, 1830, part i., page 

 306. Since then numerous applications have been made thereof. 

 .My father expressed the well-founded desire that in the astro- 

 nomical almanacs formulae might be given similar to that com- 

 municated in Nature. Charles de Littrow 



Vienna, June I 



Acoustical Phenomena 



In connection with Doppler's disputed theory of the colours of 

 stars, the illustration usually employed to assist the mind in 

 forming a conception of the hypothesis is that of the whistle of 

 a passing locomotive. The note of the whistle, which, as it 



approaches, seems shriller than its normal pitch, owing to the 

 greater number of vibrations impinging upon the ear in the unit 

 of time, falls half a tone more or less, as the engine passes and 

 recedes. To unmusical ears the difference in the note is a very 

 doubtful fact, only to be taken on hearsay. There is, however, 

 another fact of kindred nature to which attention has not, I 

 beheve, been generally drawn. Almost all railway engines, and 

 especially those drawing heavy goods' trains, have, owing to the 

 manner in which the valve-gearing is set, the property of pro- 

 ducing the well-known staccato puffs of steam, audible to the 

 ear as well as evident to the eye. Anyone who will listen to 

 these puffs as the train dashes by will be aware of a very distinct 

 and well-marked change in their apparent rapidity of succession 

 at the moment of passing. So distinct is the change that almost 

 invariably the first effect on the mind is the illusory suggestion 

 that the train has suddenly slackened speed. This change is 

 heard best at night, and when the passing train is a heavy one, 

 not running too quickly. It cannot fail to be appreciated even 

 by non-musical ears. As an illustration of a scientific principle 

 it is, perhaps of the greater value, as a popular error seems to 

 exist on the subject of the change of the note of the whistle, to 

 the effect that the lowering in pitch is very gradual during the 

 approach and recession of the engine, an opinion obviously 

 incorrect if the observer be close to the train. 

 London, June 7 S. P. Thompson 



Giant Tortoises 



In Nature, vol. xiv. p. 60, it is stated that Commander 

 Cookson, of H.M.S. Petrel, is bringing home two live specimens 

 of the giant tortoise of the Galapagos ; that ij their food lasts, 

 and if they are not killed by the cold off Cape Horn, they will 

 be the first specimens seen alive in this country. 



Even should the tortoises survive the two ifs above given, 

 they will not be the first living specimens seen in this country. 



A large speciu en brought from the Galapagos Islands by one 

 of the ships of the late S. R. Graves, M.P,, lived in good 

 health for nearly ten years in our Dublin Zoological Gardens. 



This animal was examined, after death, by Dr. Giinther, who 

 states that it is not identical with the Indian species, as supposed 

 by former naturalists. Samuel Haughton, 



Secretary Royal Zoological Gardens, 

 Dublin 



Trinity College, Dublin, June 2 



Photography of the Loan Collection Apparatus 



The Loan Collection of Scientific Apparatus at South Ken- 

 sington contains many apparatus, as for instance the first air- 

 pump of Otto von Guericke, the first boiler of Papin, the first 

 locomotive, &c. , which for the friends of science will ever be of 

 great historical interest. Therefore I cannot refrain from ex- 

 pressing the wish that opportunity should be given to take photo- 

 graphs of convenient size of some of the most interesting appa- 

 ratus. I believe many visitors will feel with me greatly gratified if 

 such a more enduring remembrance could be taken home ot an 

 exhibition that perhaps for ever will remain unequalled. 



The Hague, June 12 L. B. 



ABSTRACT REPORT TO ''NATURE" ON EX- 

 PERIMENTA TION ON ANIMALS FOR THE 

 ADVANCE OF PRACTICAL MEDICINE 



THE courteous request of the editor of Nature that I 

 should contribute to his pages an abstract of my 

 experience of the value of experimentation on animals and 

 on the most useful applications of that method of research 

 to the alleviation, directly or indirectly, of animal 

 suffering in all the higher classes of animals is responded 

 to in the subjoined notes. 



I have already expressed my views on this subject on 

 two occasions at large pubhc meetings of the Royal 

 Society for the Prevention of Cruelty to Animals, and in 

 1 862 I made a report on the same subject to the inde- 

 fatigable secretary of that society, Mr. Colam, which 

 report he has recently published, and which on the points 

 it refers to is in harmony with the conclusions of the late 

 Royal Commission. I have not, however, entered into 

 ! the discussion that for some months past has been in 



