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NATURE 



[August 21, 191, 



work of an educational expert who has certain 

 ideals, and does not hesitate to show how far exist- 

 ing- conditions differ from them. Strong- opinions 

 are given on the vexed question of the London 

 hospital medical schools, and on the constitution 

 of London University. How far the recommenda- 

 tions are practical is a question that must be left 

 for the authorities concerned to decide. It is 

 certainly desirable that London as a teaching 

 centre of medicine should not occupy a position 

 inferior to the great schools of Berlin, Vienna, and 

 Paris. 



Whatever we may think of some of the author's 

 criticisms, one cannot but admire the ability and 

 thoroughness with which he has collected informa- 

 tion and drawn up his report. Educationists 

 generally, and medical teaching authorities in par- 

 ticular, owe a debt of gratitude to the Carneg-ie 

 Foundation for the Advancement of Teaching. 



LIOUID CRYSTALS AND THE X-RAY 

 WORK. 



IN two memoirs contributed to the current 

 volume of the Verhandlungen cles Natur- 

 wissenschaftlichen Vereins, Karlsruhe, Prof. O. 

 Lehmann gives a valuable summary of his well- 

 known researches on the so-called liquid crystals, 

 and reviews the proofs now available of molecular 

 structure and of the operation of molecular forces, 

 and especially the tangible proofs of the actual 

 existence of molecules. Naturally, the most inter- 

 esting part of such a communication from Prof. 

 Lehmann is the expression of his views concern- 

 ing the most recent of such proofs, afforded by 

 the experimental work of Laue, Friedrich, and 

 Knipping with X-rays and crystals at Munich and 

 Zurich. The events leading up to this remark- 

 able development are clearly indicated, and their 

 individual significance emphasised. From the 

 initial stages of the kinetic theory of gases in the 

 days of Count Rumford and Robert Mayer — the 

 former of whom was connected with Munich, and 

 is there represented by a fine statue — to the reflec- 

 tion of X-ray electromagnetic waves from the in- 

 visible parallel planes of atoms in the interior of 

 a crystal, and the impression of the systematic 

 symmetry of the crystal on a photographic plate 

 by the reflected rays, is a long step. 



It will be with universal consent that Prof. 

 Lehmann hails this new work as of richest con- 

 sequence not only to crystallography, but to 

 general physics. He considers it the first practical 

 proof of the existence of those molecular forces 

 which he has so long contended for as causing 

 the deposition, layer upon layer in regular order, 

 of the chemical molecules in their erection of the 

 edifice of a crystal — that is, in the production 

 of a three-dimensional grating or "space-lattice." 



One of the surest sig-ns of the magnitude of 

 the discovery made at Munich is the fact that the 

 experiments, as on the occasion of the discovery 

 of radium, are being repeated and extended by 

 numerous workers all over the world, as the 

 columns of Nature, in which many of the results 

 NO. 2286, VOL. 91] 



have been described, have lately abundantly testi- 

 fied. 



It is a generally accepted maxim amongst men 

 of science that the pioneer of a new discovery 

 should be permitted to work out undisturbedly 

 its further development, and it is sincerely to 

 be hoped that Prof. Laue and Drs. Friedrich and 

 Knipping will be able to carry their work to its 

 logical conclusion. The bearing of the discovery on 

 Prof. Bragg 's theory of X-rays has, however, fully 

 justified its further independent investigation by 

 him and by his son, Mr. W. L. Bragg, who has 

 crystallographic knowledge, and has added very 

 considerably to the subject, both by further experi- 

 ments and by an explanation which agrees with the 

 crystallographic facts in a most remarkable 

 manner. There are indications that the near 

 future will see a surprising further development 

 in the direction of arriving at the absolute dimen- 

 sions of the cells of the space-lattice — that is, 

 of the actual distances separating the chemical 

 atoms, thus converting the topic axial ratios, 

 which have been so useful a conception for afford- 

 ing us the relative dimensions of the cells in 

 related compounds, into absolute spacial values. 

 Moreover, the dimensions of the material parts of 

 the atoms themselves appear likely to be also 

 determinable within definite narrow limits, for the 

 reflector, the atom, must be larger than the wave 

 reflected, and it is now clearly proved that an 

 ordinary reflection, and not a diffraction effect, is 

 in question. 



Another secondary result is that the intensity of 

 the reflection is proving a direct function of the 

 density with which the atoms are strewn in the 

 reflecting plane, thus affording us an experimental 

 means of carrying out Prof, von Fedorow's quest 

 for the primary facial planes, so as to arrive at 

 a proper descriptive setting for the crystal ; for 

 these primary planes, sometimes obscured by for- 

 tuitous better development of other planes on the 

 exterior of the crystal, are invariably those most 

 densely strewn with the atomic points. 



For a discussion of the physics of the whole 

 subject, especially as regards the position im- 

 mediately before the Munich discovery, the two 

 memoirs of Prof. Lehmann forming the subject 

 of this notice may with advantage be consulted. 

 A brief abstract of some of the most recent work 

 of Mr. W. L. Bragg will be found in the report 

 of the proceedings of the Mineralogical Society 

 of June 17 (see Nature of June 26, p. 441). 

 A. E. H. Tutton. 



THE PILTDOWN SKULL. 



A MONG the questions discussed by the anatomi- 

 ■L *■ cal section of the International Congress of 

 Medicine was the date and reconstruction of the 

 famous Piltdown skull. At South Kensington the 

 fossil portions of the skull have been put together 

 by Dr. Smith Woodward so as to represent a 

 being partly ape, partly human, and named 

 Eoanthropus davosqnii. From this model the 

 brain gives a capacity of 1076 c.c. — an amount 



