April lo, 1879] 



NATURE 



529 



two procumbent teeth rest upon a pad or projecting palate 

 which rises from the inner base of the upper incisors, and whose 

 surface is nearly upon the level of the edges of the upper teeth 

 themselves ; the lower incisors, therefore, are only brought into 

 contact with the upper incisors by protruding the jaw forward. 



I have, moreover, examined many specimens of the Macropus 

 major, or kangaroo, and of varieties of the Halmaturus known 

 as wallabies and pademelons, when they have been mortally 

 wounded and under the influence of the spasmodic muscular 

 contractions which occur at the point of death, and I have re- 

 peatedly found that they will alternately open the two incisors 

 to their full extent, and unite them again with the energy which 

 characterises all the muscular movements of an animal in its 

 death-struggle. 



If a small object, for instance the blade of a knife, is inserted 

 between the teeth when fully extended, the animal will imme- 

 diately grasp it with its incisors, which he will do without closing 

 the jaw, showing that the movement is not absolutely dependent 

 upon the action of closing the jaws, although, as I have said 

 above, I believe it usually accompanies it. 



The Phalangists or Australian opossums closely resemble the 

 macropidse in their dental formation, but they possess par- 

 tially-developed canines in the upper jaw, whilst the latter have 

 none in either jaw except in very early life ; but although these 

 opossums have their two procumbent incisors similarly situated, 

 they probably do not possess the power of utilising them in the 

 same manner ; I have examined some specimens, but have failed 

 so far to find more than the looseness of connection at the sym- 

 physis referred to by Prof. Owen. 



In the genus which is represented by the Phascolarctos or 

 native bear of Australia, which possesses the same lower incisors 

 but distinct canines in the upper jaw, this arrangement is cer- 

 tainly wanting, as the rami of the lower jaw are firmly united. 



This remarkable formation of the lower jaw of these kanga- 

 roos and wallabies is possibly an interesting instance of the 

 retention of a construction, and of a set of muscles in a class of 

 animals which have constantly required their aid to sustain life, 

 which in other families of the animal kingdom have become 

 rigid by ossification and cartilaginous formations, and by atrophy 

 of the muscles in consequence of disuse. 



The great plains and deserts over which these marsupials 

 wander in search of food affurd an exceedingly precarious sup- 

 ply of pasture in consequence of droughts and bushfires, which 

 not unfrequently follow a superabundance of herbage. These 

 animals, by means of their procumbent teeth which they make 

 use of as shears, are thus enabled to cut off any green shoots or 

 half-buried remains spared by a scorching sun, and obtain 

 nourishment where any grass-feeding placental would certainly 

 starve. 



It is in consequence, I believe, of the power which is by this 

 means given to these marsupials of eating scanty pasturage 

 closer to the ground than any other animal, that in the great 

 pastoral districts of New South Wales and Queensland it has 

 been found that they are far more destructive of food than any 

 stock that can be put upon the land, and in places where walla- 

 bies and pademelons are exceedingly numerous, it is noticeable 

 that the native grasses in the particular localities which they 

 frequent become completely destroyed, and that such places 

 remain ungrassed until fresh seed is scattered over them by the 

 winds. Henry Weld Blundell 



Gordon Downs, Queensland, December 5, 1878 



Measuring the Velocity of Sound in Air 



The following simple way of arriving at the velocity of sound 

 in air occurred to me lately : — Standing on a straight staircase 

 between two blank walls (brick, and papered), which I find to 

 be 32J inches apart, I clap my hands. The effect from each 

 clap is a brief musical sound, metallic in character, and of quite 

 appreciable pitch. It arises, doubtless, from the disturbance 

 travelling to and fro between the walls. The pitch I find to 

 be, as nearly as possible, G sharp (in the fourth space). Now, 

 the number of complete vibrations per second, corresponding to 

 this note, seems to be about 205 (see Deschanel's "Natural 

 Philosophy," p. 820). This implies that the disturbance, when 

 I clapped my hands, made 410 excursions across the >pace per 

 second. Consequently, 410 x 324 = 13,325 inches = 1,100 

 feet. This is exactly the number Deschanel gives as the velo- 

 city of sound in air at 50° (approximately our mean annual 

 temperature). M. 



Snow Flakes 



Whilst walking home on March 26, about one in the morn- 

 ing, snow began to fall very gently ; but instead of the UMial 

 powdery or feathery appearance, each flake consisted of a dis- 

 tinct plate, in some cases perfect six-pointed crystals. I mea- 

 sured some of them, and the largest were as much as five-eighths 

 of an inch across. On taking up a handful the appearance was 

 still more remarkable ; instead of the white opaque body one 

 usually sees, the mass was pearly and semi-transparent, and so 

 strongly resembling boracic acid, that I should have had some 

 difficulty in distinguishing a handful of each substance by sight 

 alone. 



Near the lamps the effect was very beautiful, more especially- 

 when the road became covered, luminous points appearing in 

 all directions, which scintillated like stars as one walked alon;^, 

 whilst many of the falling crystals reflected iridescent hues on 

 nearing the ground. 



When out of the town I ignited a piece of magnesium wire, 

 and the effect was most brilliant. 



It was a cold, dull night, barometer falling. 



Burton-on-Trent PjiANK E.,Lott 



Rats and Water Casks . -, ., 



In 1840, in a voyage from Sydney, via Madras, t& London, • 

 about three weeks after leaving the latter, it was found that a 

 number of water-butts, on their heads in the between-dee ks, 

 were leaking. On examining them we ascertained that as many 

 as ten or twelve butts had been perforated by rats; three or four 

 were entirely empty from the leakage so caused, while the re- 

 mainder contained ullages from about half to a few gallons. In 

 every case the stave had been eaten through just above the 

 chime hoop, and those which had been apparently most recently, 

 operated on had only been perforated so as to cause a slight 

 weeping, while the empty ones showed an opening as large as 

 an ordinary vent-peg hole. The rest of the voyage a tub placed 

 in the square of the main hatchway was kept constantly supplied 

 with water, besides one or more square tins of water on the 

 main deck. 



In the above voyage we stayed a week in Madras, and in 

 loosing the foretop-gallant-sail on leaving, a rat and five or six 

 young ones fell to the deck ; and the sail was found to be so 

 much eaten and full of holes, made to form and line the nest, 

 that the sail had to be unbent and replaced. 



Gurnet Bay, March 31 E. J. A'CouRT Smith 



P.S. — The ship was the Cornwall, East Indiaman, Capt. 

 Cow. 



HEINRICH WILHELM DOVE 



PROF. HEINRICH WILHELM DOVE was bom at 

 Liegnitz, Silesia, on October 6, 1803, and at the age 

 of eighteen passed from the schools of that town to the 

 Universities of Breslau and Berlin, where for the next 

 three years he devoted himself assiduously to the study of 

 mathematics and physics. In 1826 he took his degree of 

 Doctor of Philosophy, his thesis on the occasion being 

 an inquir)' regarding barometric changes ; and it is further 

 significant of his future life-work that his first published 

 memoir was a paper on certain meteorological inquiries 

 relative to winds, these two subjects holding a first place 

 in the great problem of weather-changes. 



Dove began his public life as tutor and Professor at 

 Konigsberg, where he remained till 1829, being then in- 

 vited to Berlin as supplementary Professor of Physics. 

 His strikingly clear-sighted, bold, and original intellect 

 turned instinctively to that intricate group of questions 

 in the domain of physics which comprise the science of 

 meteorology, and his success in these fields as an original 

 explorer was so marked and rapid that he soon achieved 

 for himself a seat in the Royal Academy of Sciences, and 

 some time thereafter was raised to the distinguished 

 position of the Chair of Physics in the University of 

 Berlin. 



Among the scientific and fashionable circles of Berlin 

 he took first rank as a lecturer, the combined qualities of 

 accurate science, fine imagination, lucidity of style, com- 



