August ii, 1910] 



NATURE 



187 



iS inches in height and 6 inches in thickness, while the 

 total length of the intervening run was approximately 

 25 inches. In this run were placed thirteen flakes of lime- 

 stone, together with about the same number of small green 

 pods and a few beans, but no feathers or shells. The 

 nests, which were built of twigs and placed in casuarina 

 trees near the run, each contained a pair of heavily 

 scribbled eggs. 



Vox several years past Messrs. Baldwin Spencer and 

 J. J. I'letcher have been studying and describing a large 

 collection of Australian earth-worms, but in many instances 

 it has been found impossible to decide on the proper generic 

 position of the species. Before the classification can be 

 considered final, a large amount of anatomical investiga- 

 tion is essential, and this work is being undertaken by 

 the scientific staff of Melbourne University. Four papers, 

 two by Miss G. Buchanan, the third by Miss F. Bage, 

 and the fourth by Miss J. W. Ruff, embodying some of the 

 results of this work are published in vol. xxii., part ii., 

 of the Proceedings of the Royal Society of Victoria. Miss 

 Bage, who treats of the structure and arrangement of the 

 nephridea, states that these organs are subject to great 

 variation in the different groups, and will probably be 

 found of great value lor systematic purposes. 



.\mong other articles on local natural history in the 

 March issue (vol. i.. No. 5) of the Queensland Naturalist, 

 special interest attaches to one describing a visit paid by 

 Mr. G. H. Barker in September, 1909, to the reserve at 

 Gold Creek, where numerous kinds of birds were observed. 



The writer of these notes has been favoured with a 

 cutting from the Argentine journal La Nacion of April 15 

 containing an account of a newly discovered skull of the 

 gigantic glyptodont D.-edicurus, with the previously un- 

 known deripal head-shield in position. The skull appears 

 to have been found in association with the skeleton, thus 

 making the fourth more or less nearly complete example 

 of the bony framework of this gigantic species. 



RAINFALL OF RHODESLi AND AUSTRALL4. 

 'pO the Proceedings of the Rliodesia Scientific Associa- 

 ^ tion (vol. viii., part iii., igog) the Rev. E. Goetz, 

 S.J., contributes a very valuable discussion of the rainfall 

 of Rhodesia, based upon observations at sixty-three 

 stations. Fifty of these are in southern Rhodesia ; the 

 conclusions therefore apply more particularly to the country 

 between the Zambezi and the Limpopo (long. 27°-33° E.). 

 The tables contain monthly and yearly amounts from the 

 actual observations. The longest series is for Hopefountain 

 (nineteen years), and the averages at most of the other 

 stations have also been reduced to this normal by the 

 usual method. .An annual rainfall map shows clearly that 

 the amounts near the Portuguese territory vary from 45 

 to 30 inches, and decrease westwards to 20 inches ; but to 

 the north-west (north of the Zambezi) the unreduced 

 averages increase to 30 inches and above. There are 

 some closed areas of high rainfall in southern Rhodesia 

 which, the author assumes, will probably disappear with 

 the returns of a larger number of stations. The rainfall 

 for seasons, and for short periods at some selected stations, 

 is dealt with in considerable detail. There is also an 

 interesting discussion of rain and drought cycles ; the 

 nineteen-year cycle, based on the periodic movement of 

 the high-pressure belt, recently proposed by Colonel H. E. 

 Rawson, seems (the author thinks) to promise good 

 results. 



Bulletin No. 4, issued by the Australian Commonwealth 

 Bureau of Meteorology, includes, inter alia, tables of per- 

 centages and mean monthly and annual average rainfall 

 for each colony and for Tasmania. These values are 

 transferred to a map consisting of miniature " graphs," 

 showing very clearly the mean monthly percentages and 

 other details. One of the several useful appendices shows 

 the hourly distribution of rainfall and frequency of showers 

 in most of the capital towns for a year ending June 30, 

 iqoq. The text of the bulletin gives an interesting account 

 of the broad features shawn bv the maps, viz. that nearlv 

 the whole of tropical .Australia receives the bulk of its 

 rains during the period of the year when the convectional 

 action in the interior of the continent is at its maximum. 

 In the central latitudes, although the monsoonal influence 



NO. 2128, VOL. 84] 



still predominates, the colder months are under the in- 

 fluence of V-shaped depressions which skirt the southern 

 shores during the winter and spring seasons. In VVestern 

 Australia the maxima occur in the early and mid-winter 

 months over the whole of the western and southern dis- 

 tricts. In the agricultural areas of South Australia the 

 winter and spring maxima are very marked, but in the 

 far north the monthly values are very erratic. The pro- 

 nounced feature of winter rains over South Australia and' 

 the western part of Western Australia is maintained in 

 the western slope districts of New South Wales, but is 

 obscured over the Victorian areas south and east of the 

 mountain ranges by the disturbing character of the country. 

 The same peculia'rities affect the central, western, and 

 northern interior of New South W'ales. 



THE CHEMICAL SIGNIFICANCE OF CRYSTAL 

 STRUCTURED 



LARGE numbers of chemical substances occur on the 

 earth's surface as definite geometrical forms bounded 

 by plane faces ; these polyhedral shapes are called crystals. 

 Inspection of the crystal forms assumed by mineral sub- 

 stances shows that, roughly speaking, each crystalline 

 substance affects some specific geometrical shape which is 

 characteristic for the material ; further that, whilst crystals 

 of any particular mineral attain vastly different dimensions 

 and are bounded by planes which vary greatly in relative 

 area, one geometrical feature remains constant. The angles 

 between corresponding pairs of faces on any two crystals 

 of the same substance are the same, notwithstanding the 

 existence of difference in size or in relative face magnitude 

 between the two crystals. The constancy of interfacial 

 angle amongst crystals of the same substance is a law of 

 naltire, and has been amply demonstrated by the very 

 careful crystallographic measurements made by Tutton 

 during the' last twenty years. 



It is, however, not essential to study mineral substances 

 alone in order to obtain a knowledge of the laws govern- 

 ing crystal growth. Great numbers of laboratory products 

 can be caused to crystallise by condensation from some 

 fluid condition ; thus the crystals of various alums exhibited 

 were obtained by slow evaporation of aqueous solutions of 



The examination of a crystal shows that many of its 

 physical properties differ according to the direction iri the 

 crystal in which the property is determined; the hardness 

 of" crystals, the speed at which light travels through them, 

 and manv other properties, are commonly dependent on 

 thf direction in which the material is examined. 



The dependence of crystal properties on direction 

 indicates the most essential feature of the crystal to be a 

 definite and orderly arrangement of its ultimate particles ; 

 this arrangement is referred to as the crystal structure. 

 Further evidence that crystals possess an arranged struc- 

 ture is furnished by the observation that crystalTTsation is 

 not necessarily a spontaneous process. Thus, on melting 

 benzophenone' and r.;pid:y cooling the clear molten mass, 

 the liquid state is retained for many hours at a tempera- 

 ture far below the normal melting point of the compound. 

 But on inoculating the liquid with a trace of crystalline 

 benzophenone, crvstallisation immediately commences and 

 rapidly becomes complete. The introduction of a small 

 particle of crystalline or arranged material into the liquid 

 mass provides a nucleus upon which the molecules are 

 .able to deposit themselves in a similar crystalline arrange- 

 ment ; the process thus started quickly becomes propagated 

 throughout the entire mass. The lack of spontaneity in 

 the process of crvstallisation leads occasionally to quite 

 unexpected results.' Thus tetrahydroquinaldine has been 

 known for manv years, and has been prepared by numbers 

 of chemists. It lias always been obtained as_ a liquid, and 

 has never been supposed capable of existing in the crystal- 

 line state at ordinary temperatures ; even when cooled in 

 liquid air it merely becomes a thick resin, and does not 

 crystallise. But on dissolving a few drops of it in a little 

 light petroleum, and cooling the solution thus obtained in 

 liquid air, the tetrahydroquinaldine crystallises out ; on 

 transferring a trace of the crystalline material obtained to 



1 Di^cour'se delivered at the Royal Institution on Friday, April 15, by 

 Prof. William J. Pope, F K.S. 



