124 



NA TURE 



[June 7. 1 1>94 



surroundings encourage the formation of sound teeth in a 

 sound t)ody ; but I cannot Imi think that the principal cause 

 of caries must be looked for in the food. It is plainly shown 

 by many investigators, and in the piper above referred to, that 

 caries ii rare among peoples who subsist principally upon animal 

 food ; the Esquimaux showed, among sixly-nine skulls, only 

 two cases of caries, and the largest amount of disease was 

 found among those races who lived upon a mixed or exclusively 

 vegetable diet. These results are, of course, easily understood 

 under the more accurate knowledge which we now possess of 

 'he immediate causes of dental caries. 



As to the relatiie frequency with which different teeth are 

 affected, I think statistics plainly show that it is the first molar 

 tooth of the lower jaw which is \\\a-\ prone to decay of any 

 toith in the series, and most authorities consider the second 

 lower inolar as the next in order ; with these two exceptions the 

 upper are more frequently di-eased than the lower teeth. This 

 would, however, not affect the argument, as the lower molars 

 are of course also supplied by the lifth nerve. 



Structural defects, due to inherited weakness or imperfect 

 nutrition during the dtvelopment cf the tetth, combined with tlie 

 use of soft cooked food, which is long retained in contact with 

 them, and is of a nature eminently suitable for fermentaiion, 

 give us, I think, the principal factors of decay among civilised 

 racfs. 



While allowing the influence of nerve strain in early child- 

 hood, and as a factor in hereditary transmission of defective 

 structure, I fail to see how it can influence teeth already 

 formed. J. Howard Mummery. 



May 27. 



Centipedes and their Young. 



Referring to Mr. Urich'.s letter in your issue of April 5, I 

 send the following remarks, which no doubt will interest some of 

 your readers. During my eight years' residence in Guiana, I have 

 frequently had brought to the museum, centipedes of from 5-S 

 inches in length, carr)'ing their young clasped by means of their 

 legs to all parts of the underside of the body, though generally 

 the young have been clustered in dense masses rather than scat- 

 tered. In their very early stages the young are closely clustered, 

 and seem quite unable to clasp their parent in turn, but later 

 they become very restless, and will be seen moving about inde- 

 pendently, and when clustered by the action of the parent they 

 are incessantly changing their position in the cluster. When 

 the young are thus bunched together, the body of the parent is 

 coiled upon itself at that pan ; and the contrast between a 

 centipede in this position, and a scorpion carrying her young 

 upon her back, just as a small opossum does, is a very marked 

 one. 



I had imagined that this habit of the centipedes was widely 

 and generally known ; and indeed Packard ("Guide to the Study 

 of Insects," p. 674) remarks that " Wood also states that the 

 femal; guards her young by lying on her side, and then coiling 

 her body passes them along by a rapid cilia-like action of her 

 feet, thus arranging them satisfactorily to herself" This is but 

 a very terse description of what will be observed when one 

 di«turb» a centipede and the arrangement of her young about 

 her body. 



As remarked by Dalton (" History of liritish Guiana," vol. ii. 

 p. 267), the centipedes •' lay their eggs in clusters hke little 

 t>erries on the ground, and the female chooses an obscure place 

 for this purpoie, as under llower-pols, where she can remain 

 until the eggs are haichcd," Centipedes are not seldom met 

 with in such obscure and uniformly moist place; as under flower- 

 pots and tub!, or boards and shingles, with their eggs clustered 

 at described. 



With regard to the disappearance of the young ones from 

 the box forwarded from 1'rmidad to London, the most likely 

 explanation is that they were eaten by the parent. If the 

 parent centipede be kept wiih the young ones, and led 

 unf d for n day or two, it will l)e observed to feed quiie 

 Icisuiely and greedily at limes on its young. This I have 

 witnessed ilirectly in three separate ca«s where Ihey had been 

 kept unfed in a long k'»*« j" i" the museum. The most desir- 

 able food for ceniipcdes in the tropics, I may incidentally 

 remark, is the cockroach. J. J. QUEI.CII. 



The Muicum, liritish Guiana, May 10. 



NO. 1284, VOL. 50] 



The Penetrative Power of Bullets. 



I HAVE been stimulated by the recent trials of the bullet- 

 proof cuirass, to try a few experiments on the subject. I wil 

 only mention one experiment, which 1 made this morniui;. 

 assisted by several members of the junior scientific club here. 

 It occurred to me that if the energy of the bullet could he 

 made to act at rather a large angle to its line of flight, its pene 

 trative power would be dimmished. To elTect this, I arranged a 

 number of soft iron rods J inch in diameter and 5 inches long, 

 side by side and touching a piece of deal board ; on these another 

 layer was placed, so that one of the upper rods touched two cil 

 the under ones. A sheet of thin rubber ,',- inch thick, placed on 

 this, separated it from a similar combination attached lo it at 

 right angles ; and the whole formed the target. Tne rifle used 

 was a Winchester, 22 bore, carrying a long bullet. At a distance 

 of 20 feet the bullet penetrated 5 inches of hard pine with cer- 

 tainty ; but when the bullet tired at the same distance hit uiy 

 rod target, it failed to penetrate even the first layer, but only 

 drove tne upper rods aside nearly at right angles to the line of 

 flight. The next experiments will be made with heavier 

 materials and larger shot. Possibly a similar arrangement, but 

 of large steel cylinders, might make a satisfactory barrier lo 

 the shot of big guns. Fuedkrick J. Smith. 



Millard Engineering Laboratory, O.'ilord, June I. 



The Garhwal Landslip. 



Liii' mc point out that the paragraph on p. 109 of Nature 

 for May 21, stating that the landslip that had occurred in the 

 Garhwal district in the Himalaya, blocking up the Bireh 

 Ganga river, had burst, causing the loss of many lives, is 

 erroneous. The catastrophe reported from India had reference 

 to a locality in Kulu, and not lo Garhwal, the two being several 

 hundred miles apart. 



An accurate description of the Garhwal landslip will, I hope, 

 be shortly published in the Koyal Geographical Society's 

 journal. The obstruction is being carefully watched, and the 

 water has not yet lopped it. There is, I ihink, considerable 

 reason to anticipate that no great destruction will be caused at 

 this place, as ihe landslip is of such vast dimensions as to make 

 it almost impossible that it should be carried away in a manner 

 to give rise to a great and sudden flood. It is upwards of a 

 mile in length and two-thirds of a mile wide, rising about 900 

 feet above the original level of the valley, and being largely 

 composed of enormous masses of rock. 



June I. K. Strachey. 



Research Work. 



May I be allowed lo suggest that it would be a great help to 

 many interested in science if an authorised body, such as the 

 British Association, were occasionally 10 indicate paths of re- 

 search work in difterent branches of science, especially in 

 physics and cliemislry, which would olTer a reasonable prospect of 

 leading to useful results? Many, especially among tho^e engaged 

 in educational work away from London, have not the adv.intage 

 of continued intercourse with the leaders of scientific thought 

 which would give them the opportunity of forming a judgment 

 themselves, and the fear of having been forestalled by others 

 makes them hesitate to devote the lime required for a sustained 

 course of experimental research. Wiihin the writer's experience, 

 men whose juilgment carries great weight do not individually 

 feci inclined to give advice which they consider ought primarily 

 10 be devoted to the. id vanceuienlof their own students. The advan- 

 tages of a laboratory, of leisure lime, and of a desire to a Id their 

 quota lo the slock of knowledge are not, by the wise, throwr* 

 away, but a great deal of energy, at presLMit more or less dissi- 

 pated, might be diverted into more useful channels if the above 

 suggestion were carried out — offering each one the oppo.'tunity 

 of choosing that particular line of research which most nearly 

 satisfies the c inditions In which he is placed. The idea might 

 l)e still fuither developed by associalin.; workers together for a 

 common end, even at the risk of not being able to eliminate ihe 

 personal factor. W. G. Wooii.coMiiE. 



liirmingham, May 31. 



A Daylight Meteor. 



The following accjunt of a meteor, seen by me in full day- 

 light, may be of interest lo rei lets of NatUKK. It was written 

 a few hours afier the meteor appeared. 



