November 21, [918 



NATURE 



233 



painted in whiting and water that has survived 



for more than twenty-five years, in -pit'- <>f the 



window-cleaning thai it has been subjected to. Hi 



suggests thai the effect is due to molecular changes. 



Mr. Julius Rheinberg says that hi- experiments "madi 



during the last years on the introduction of metals 



into the surface-layer "f glass have convinced him 



anil more that we should regard glass as a 



substance full of ultra-microscopic pores." He sug- 



- that material left in these pon -, which would 



cleaning processes, may form the 



nuclei or condensation centres when the latent image 



i. rendered visibli . Mr. Rheinberg is well known 



among men ol science interested in microscopical and 



1 graphical matters, and as he is the maker of the 



ules and micrometer and other scales exhibited 



tie- British Scientific Products Exhibition recenth 



arranged by the British Science Guild, his opinion is 



iecial interest. Some of these scales, etc., have 



gradations made photographically in untarnishable 



1 in tin- surface-layer of the glass itself, and thus 



no cover-glass to protect them. 



he stoppage of supplies of organic developing 

 - from Germany led to the supply ol man; 

 'metol substitutes." Several of these have been 

 lined in tin- research laboratory of the Eastman 

 : Co., and tnev have communicated their methods 

 of analysis and some typical results to the British 

 Journal 0) Photography for November 8. Some con- 

 I a small proportion of metol. One contained 

 metol 10 per cent., hydroquinone 1N5 per cent., the 

 resl being cane-sugar and sodium sulphite. Another 

 -imph pyrogatlol with three times it^ weighl of 

 sodium sulphite. Some were boldh labelled "metol" 

 ! "substitute." Two such did not 

 tin a trace of methylated product, though one was 

 labelled "hydrochloride of methyl-p-amino-m-cresol, 

 cent, pure." Another was half 

 hydroquinone, and contained sodium sulphite, potass- 

 ium iodide, and sodium carbonate. Of developing 

 • that did not claim any special relationship to 

 I Olie was half starch and moisture. There is also 

 given a long list of adulterants and u~e|e*s additions 

 that Dr. II. T. Clarke, the analyst, has found in 

 variot: agents. Although such 



stuffs a- those mentioned may be on the market, there 

 is no need to use them, because reputable firms are. 

 making the genuine developing agents and marketing 

 them under their proper names. Rut it behoves thosi 

 use developers to he on their guard. 



A f»w months ago Messrs. Pictet and Sarasin 

 bed tie- production of laevoglucosane by the dis- 

 tillation of cellulose or starch under diminished pres 

 sure. This body is of interest, since it can be con- 

 into (/-glucose and tie me into alcohol. In 

 ! 1 (No. 3) M. Pictet shows that 

 the reverse process is possibli up to a certain point, 

 laevogl idily transformed into dextrin 



by re-polymerisation. This change is brought about 

 mplj melting the laevoglucosane in the presenci 

 of platinum black, which acts as a catalyst; the 

 formation is complete in a few minutes. As 

 1- the product, this approximates to certain of 

 '• xtrins, but has a notably lower rota- 

 In the same number of the Acta there 

 ither interesting instance of catalytic action. 

 M. F. Reverdin shows that the benzoylatioin of certain 

 aromatic derivatives is greatly facilitated by carrying 

 out the operation in the presence of a small quantity 

 of sulphuric acid. Resorcin, alizarin, amino-anthra- 

 quinones, and trinitro-/>nra-anisidino are some of the 

 compounds "hirh can thus be n Oyfated. 



XO. 2560, VOL. I02] 



OUR ASTRONOMICAL COLUMN. 



Tin; Planei Saturn.- This attractive telescopic 

 object is now coming favourably into view in the 

 evening hours, rising on November 25 at ioh. 34m. 

 and on December 25 at Mi. 35m. p.m.' The southern 

 surface of the rin^ ;„ visible, fan the angle subtended 

 by the minor axis is growing less as the planet V 

 motion is directed southwards. 



Surface phenomena, of somewhat similar nature to 

 those affecting Jupiter, are visible on Saturn, but are 

 more difficult to detect, and probable less frequent 

 in their manifestation. Further studv of the markings 

 iirable, and especially with regard to their rates 

 of motion in different latitudes. Mr. Denning writes 

 that from a number of white and dark spots placed 

 in the planet's north temperate zone in 190; he 

 deduced a mean rotation period of ioh. 37m. 56.4s. 

 I his differs considerably from the period ascertained 

 from a white equatorial spot seen by Prof. Asaph 

 Hall in 1S76-77, which gave ioh. 14m. 2j-Ss. In 

 1703-04 Sir W. Herschel made some observations of 

 ertain inequalities in a southern quintuple belt on 

 Saturn, and found the period ioh. 16m. 044s. If 

 my spots or other irregularities in the belts are 

 detected during the few ensuing months, their transit 

 times across the central meridian should be taken 

 with the view of redetermining the rate of rotation. 

 During the remainder of the present year the planet 

 will be in a position about 1A from Regulus in Leo, 

 and the configuration will he an attractive one for 

 naked-eve observers. 



The Origin of Comets. — Prof. Stromgren con- 

 tributes an article on this subject to Scientia for August 

 last. For some years past he has been studying the 

 effect of planetary perturbations on those comets for 

 which hyperbolic orbits have been found ; his con- 

 clusion is that the excess of the eccentricity above 

 unity can in all these cases be explained by the per- 

 turbations — in other words, that the primitive orbit 

 was_ elliptical, and that the comets in question are 

 original members of the solar system, not visitors 

 from without. This conclusion is indeed fairlv 

 obvious a priori, since the relative velocities of the 

 stars are of the order of several miles per second, and 

 any body entering the sun's sphere of influence with 

 such a speed would have an orbit of a decidedly hyper- 

 bolic character, whereas the eccentricity of the orbits 

 in question is very little in excess of unity. 



The remainder of the article is occupied bv specula- 

 tions on the cause of the prevalence of elliptical orbits 

 of immense periods; the conclusion is that the matter 

 now forming the planets and comets was formerly 

 distributed as a diffused nebula over a region im- 

 mensely larger than that bounded l>\ the present plane- 

 tary orbits, but excessively tenuous in the outer portions ; 

 any slowly moving fragments in these outer regions 

 would approach the centre under gravity, their orbits 

 being long ellipses, almost parabolic. Prof. Stromgren 

 makes a novel suggestion to explain the absence of 

 cometary matter in the interstellar spaces. It is now 

 generally accepted that there is a tendency to equi- 

 partition of energy among the stars, the smaller masses 

 having the greater speeds. On this view small 

 cometary masses would attain such high speeds that 

 they would be expelled from the stellar system; those 

 alone would remain that were within the domains of 

 individual st 



MtNOR Pr. \\p:ts.— The fifth planet of the Trojan 



group, discovered last year and designated 1917CO, 



reobserv'ed by Prof. Wolf on October 5. Tts 



magnitude was 14-,. Prof. Wolf has given' it the 



name Priamus. 



