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March 2, 1922] 



NATURE 



283 



enty-five to fifty years, and is effected by the 

 lection method. With proper precautions against 

 e, the Kauri forests that remain in New Zealand 

 n be so managed as to yield a rich store of timber 

 r centuries to come. The other important conifers 

 New Zealand, Dacrydium cupressinuni, D. Colensoi, 

 'odocarpus dacrydioides, and P. totara, also regenerate 

 \'igorously, and the process of their regrowth is in 

 evidence in all situations where fire and grazing are 

 excluded. 



The Moss Rose. — The origin of the moss rose is 

 the subject of a paper by Major Hurst and Miss 

 M. S. G. Breeze in the current issue of the Journal 

 'A the Royal Horticultural Society. It differs from 

 the cabbage rose {R. centifolia) only in the much 

 greater development and branching character of the 

 glands on petioles and sepals and the branching of 

 the latter. The cabbage rose has been in cultivation 

 tor more than two thousand years, and the earliest 

 record of the moss rose is from Carcassonne, in 

 southern France, where it probably originated as a 

 bud-mutation from the cabbage rose at least as early 

 as 1696. The mossy character has since arisen inde- 

 pendently from two other varieties of the cabbage 

 rose. In 1 775 the Unique Rose appeared in a garden 

 in the Eastern Counties as a tinged-white variety, 

 and in turn gave rise to the " Unique Moss " through 

 a bud-mutation in France about 1843. The Rose de 

 Meaux is a miniature variety of the cabbage rose 

 which may date from about 1637. A moss mutation 

 appeared from this in the West of England in 1801. 

 IJoth the moss and cabbage rose are sterile, and 

 tliere is little doubt that all these derivatives arose 

 from the old cabbage rose as bud-mutations. The 

 records show that at least seven bud-reversions from 

 the moss rose to the cabbage rose occurred in the 

 period between 1805 and 1873. In the half -century 

 following 1788 seventeen varieties of the moss rose 

 appeared, one of which was single and fertile and 

 extensively used in crossing. Twelve of these bud- 

 mutations are parallel to corresponding earlier 

 variations in the old cabbage rose. Bud-mutation is 

 therefore a frequent phenomenon in Rosa centifolia 

 under cultivation, and there is, as the authors suggest, 

 a direct connection between this condition and the 

 sterihty. The evidence indicates that the mossy 

 character is probably a simple Mendelian dominant. 



The Examination of Textiles by X-rays. — An 

 interesting addition to the many and varied uses 

 of X-rays in the examination of materials has been 

 developed by Messrs. Truesdale and Hayes in the 

 research laboratory of the Dunlop Rubber Co., 

 Birmingham. In the Journal of the Textile Institute, 

 vol. 12, No. II, November 1921, they describe how, 

 by the aid of radiography, they have studied the 

 movement of the threads in the canvas of a motor- 

 tyre during the several processes of manufacture of 

 the tyre. For this purpose the canvas was specially 

 woven so that every twentieth thread, both warp and 

 weft, had been previously impregnated with a heavy 

 salt. Thus the X-ray photograph reveals a series 

 of squares, the pattern being in the form of a check. 

 The most suitable salt for the purpose was found to 

 be lead chromate formed by precipitation on the yam 

 by first soaking it in lead acetate and then in 

 potassium bichromate. The X-ray plates or films 

 were placed in actual contact with the material, so 

 tliat the dimensions of the radiograph were those of 

 the canvas. In the case of a tyre the film was placed 

 mside the tyre, in contact with the first ply, and held 

 in position by spring clips. The X-ray tube was on 

 the out.side, and care was taken that the X-rays were 

 normal to the film. As the series of reproduced 

 radiographs shows, the dimensions of the sides and 

 angles of the squares are affected in some of the 



NO. 2731, VOL. 109] 



processes. By measuring predetermined squares on 

 the radiograph taken after each process the change 

 due to the previous process can be arrived at. The 

 method proves to be an effective means of ascertaining 

 whether the stretch of the canvas threads, resulting 

 from the various processes in the manufacture of the 

 tyre, is within the hmits of stretch tolerated by the 

 yam — a point of extreme importance to the tyre 

 manufacturer. 



Propagation of Earthquake Waves. — Dr. S. W. 

 Visser, of the Royal Magnetic and Meteorological 

 Observatory of Batavia, has recently issued an im- 

 portant paper on " The Distribution of Earthquakes 

 in the Netherlands East Indian Archipelago during 

 1910-19, with a Discussion of Time-tables." For 

 several years the tables in use of the times of transit 

 of the primary and secondary waves as recorded on 

 seismometers have been recognised as requiring cor- 

 rections, and both Geiger and Gutenberg in Germany 

 and G. W. Walker in this country have made definite 

 suggestions towards this end. By a detailed discus- 

 sion of the earthquakes having their origin near 

 Batavia, Visser has been able, by means of a careful 

 examination of the records obtained at distant 

 stations, to draw up new sets of tables so far cor- 

 roborating the suggestions already made, but carrying 

 out the corrections much more completely and through 

 the whole range of distances from the epicentre. The 

 corrections of the primary times of transit are most 

 conspicuous in the range from 50° to 100° arcual 

 distance, being an increase of as much as 10 seconds 

 at the distance of 60° or 70°. In the case of the 

 secondary times of transit the corrections are more 

 in evidence, being a decrease for small arcs (less 

 than 50°), an increase for larger arcs (up to 70°), and 

 a marked decrease for arcs greater than 80°. Visser 

 also discusses what seems to be the manner of pro- 

 pagation of the waves which enter the nucleus of the 

 earth, and gives general support to the views ex- 

 pressed by Knott in his recent paper on the 

 propagation of earthquake waves. In the light of 

 the corrections now supplied it will be necessary to 

 recalculate the forms of the seismic rays, especially 

 for the secondary waves. Visser fully bears out the 

 conclusion already come to that the primary wave 

 ceases to be recorded at distances greater than about 

 110°, but finds evidence of their reappearance beyond 

 140° with a retarded time of transit. 



Harmonic Development of Tidal Theory. — Dr. 

 A. T. Doodson, of the Tidal Institute, University of 

 Liverpool, has just published in the Proceedings of 

 the Royal Society (A, vol. 100, p. 305, 1921) a paper 

 on " The Harmonic Development of the Tide- 

 generating Potential." Since 1883 the development 

 given by Sir G. H. Darwin has been universally used 

 and has proved of remarkable value, but the assump- 

 tion usually tacitly made, that no terms not included 

 in his schedule need be considered in tidal prediction, 

 has been shown by work at Liverpool on tidal 

 observations to be unjustified. It was therefore 

 decided to make a new development in which, 

 in view of the possibility of terms being magnified 

 by resonance, great accuracy has been striven after. 

 All terms the coefficients of which exceed one ten- 

 thousandth of the leading term are included ; this 

 degree of accuracy is unnecessary for practical tidal 

 work, but the needs of research were also kept in 

 mind. Unlike Darwin's development, which was 

 algebraic and founded on the old lunar theory, 

 referring everything to the orbit rather than to the 

 ecliptic, the present work is essentially numerical and 

 strictly harmonic ; Brown's new lunar theory is taken 

 as the basis of the development. Many terms which 

 are too large to be ignored for modem purposes, but do 

 not occur in Darwin's schedule, have been found. 



