49Q 



NATURE 



[July io, 1913 



mean is 327 in. For a large area (about 3000 square 

 miles) no records are available. 



The annual report of the meteorological observatory 

 of the Government-General of Korea for the year 19 11 

 (Dr. Y. Wada, director) contains valuable observations 

 taken three times daily at ten stations, with carefully 

 prepared summaries. Weather conditions and special 

 occurrences are denoted by international symbols, and 

 the instruments and methods of observation are similar 

 to those at meteorological stations in Japan, and, con- 

 sequently, are all that can be desired. The absolute 

 maxima of air temperature ranged between 88-3° F. 

 at Fusan and 92-8° at Chemulpo, both in August, 

 and the absolute minima between — 16-1° at Ping-yang 

 and 15-3° at Mokpo, both in January. The yearly 

 rainfall varied from 33-3 in. at Song-chin to 76-8 in. 

 at Fusan. The largest amount of sunshine was 2642 

 hours, at Ping-yang, being 60 per cent, of the possible 

 quantity. 



A report on the Mariout district, by Mr. A. L. P. 

 Weedon.in Nos. 72 and 73 of The Cairo Scientific 

 Journal, is of much interest, both from an agricultural 

 and from a meteorological point of view. The dis- 

 trict, which consists of a long strip of land west of 

 Alexandria, was in ancient times famous for. its fer- 

 tility, but at present it is for the most part barren 

 and waste, barley being practically the only crop 

 grown, in some parts only, and this is dependent on 

 the somewhat precarious winter rains. The rainfall 

 seems to differ but slightly from that of Alexandria, 

 which averages 220 mm. '(87 in.) per annum. The 

 climate depends on the temperature of the Mediter- 

 ranean and the general atmospheric circulation, and 

 frorn numerous quotations from ancient and modern 

 writers it is concluded that there is no reason to 

 believe that either of those factors, or the rainfall, 

 has changed since Roman times. The author states 

 that the land is capable of producing more profitable 

 crops in the hands of more efficient cultivators, who 

 by the employment of scientific methods could either 

 give it a better or more regular water supply, or make 

 a better use of the existing moisture of the soil, e.g. 

 by a system of dry-farming (economising the rain- 

 water by digging trenches before the rainy season), 

 assisted by wells and cisterns, many of which already 

 exist. 



The Austrian Meteorological Institute has published 

 part v. of its valuable " Klimatographie " of that 

 country, referring to the mountainous province of Salz- 

 burg. Climatologically, Salzburg belongs to the Central 

 European district, but owing to the Alps it is subject 

 to many marked modifications. The portion on the 

 northern side of the limestone Alps, being exposed 

 to the north and north-west winds, has a decidedly 

 damp and rainy character, with the peculiarities of the 

 West European climate. But between the limestone 

 and central alpine chain lies a zone of a continental, 

 dry character, with stagnant masses of air (Luftseen) 

 in the valleys, in winter excessively cold, and relatively 

 warm in summer. In the Lungau district, Salzburg 

 participates in the rough, inhospitable climate of the 

 upper Mur vallev. The author, Dr. A. Fessler, adopts 

 in the main this general subdivision of the climatic 

 conditions in his elaborate discussion, dealing with 

 each district in great detail, and with full consideration 

 of the effects of aspect and altitude on temperature, 

 rainfall, and climate generally. The discussion is 

 based on observations made at stations connected with 

 the Central Institute, but the author is handicapped 

 bv the paucity of data in many points of climatological 

 importance; from this point of view Salzburg com- 

 pares unfavourably with other alpine districts; com- 

 plete observations for, say. twenty years and upwards 

 onlv exist for comparatively few stations. 

 NO. 2 2 8o, VOL. qi] 



GREAT ADVANCE IN CRYSTALLO- 

 GRAPHY. 1 

 CRYSTALLOGRAPHY has made such remarkable- 

 progress during the last few months, and the 

 position at the present moment is so interesting, that 

 it was considered opportune to review it in a discourse 

 from this historic lecture-table. 



Overwhelming evidence has now been brought for- 

 ward that a crystal is endowed with a definitely- 

 organised structure. 2 In the crystal of a pure sub- 

 stance we are dealing with a chemical element or 

 compound, and if with the latter it may be of any 

 grade of complexity, from a very simple binary com- 

 pound to a most highly complicated one composed of 

 a large number of atoms. If the crystal be that of 

 an element the structure is obviously composed of the 

 similar atoms of that element, while if it be a com- 

 pound we have a structure composed of atoms of as 

 many kinds as there are chemical elements present 

 combined in the substance, and in the same relative 

 proportion as is expressed by the chemical formula 

 of the substance. In the case of a compound, more- 

 over, the structure may also be considered to be that 

 of the molecules of the substance, for they or a simple 

 arrangement of a small number (group) of them form 

 the grosser units of the structure, whilst the atoms 

 are the ultimate units. 



Suppose we now represent this molecular or poly- 

 molecular grosser structural unit by a point, and that 

 such point be analogously situated within each unit. 

 The essence- of crystal structure then is that these 

 points are so arranged in space that if they are joined 

 along the three directions of space by imaginary lines 

 the latter form a "space-lattice" (German, " Raum- 

 gitter"), each unit cell of which may be conceived to 

 be the "brick" already alluded to in the earlier part 

 of the lecture, and the domicile of the chemical mole- 

 cule or group of molecules (indeed, it is immaterial 

 whether the points are considered as placed at the 

 corners or in the centres of the cells) or, in the case of 

 an elementary substance, of a group of similar atoms. 

 We may, therefore, define a crystal as follows : — 



"A crystal of any definite chemical substance con- 

 sists of a homogeneous arrangement of grosser units 

 of matter, each consisting of one chemical molecule 

 or a small group of molecules of the substance, and 

 the kind of arrangement is such that these grosser 

 units are all identically (sameways, parallel-wise) 

 orientated, and that their analogously chosen repre- 

 sentative points, one from each such grosser unit, 

 form a space-lattice (Raumgitter)." 3 



There are fourteen kinds of space-lattices, slides 

 of several of which are exhibited on the screen. 

 Three possess full cubic symmetry, two are tetragonal, 

 four are endowed with rhombic symmetry, and two 

 are monoclinic ; while triclinic, trigonal,' and hexa- 

 gonal crystals have each one space-lattice correspond- 

 ing to their type of symmetry. In everv case it is 

 the full (holohedral) symmetry of the system which 

 is present, no space-lattice possessing merely the lower 

 deeree of symmetry corresponding- to one of the so- 

 called hemihedral or tetartohedral classes of the 

 system in question. 



Now in the solid crystal, not only are the grosser 



by£T a ferSSWa th= Roya ' Inst " ution on Friday ' March '« 



2 This was very fully illustrated by numerous experiments during the first 

 portion of the discourse. 



3 Since this lecture was delivered (March 14) and printed by the Royal 

 Institution, a paper by Prof. Theodore W. Richards, of Harvard University, 

 has appeared in the Journal of the American Chemical Society for April 

 (vol. xxxv., p. (3 8t\ in which he shows that his theory of compressihle 

 atoms leads to crystal uiyts of precisely the molecular or polymolecular 

 character described in this lecture. He suppos-s such crystal units to be the 

 entities necessary to relieve metastahle supersaturation and their centres to 

 form the points of the crystal space -grating, assumptions with which the 

 lecturer obviously fully concurs. 



