KNo\vij:i)r,i.. 



Novi;Miti:i(, 1012. 



hv IK1 im-aiis tirl.iiii tlial wd stars, tlu)ii;;li |)i<il)al)ly 

 codlcr, arc older tlian wliitc ones — they may be 

 growing hotter ; nor is it In' any means necessarily 

 the fact tliat our own Moon once fmnu d |i;nt of an 

 intensely-lieated mass. However, tin- trndcncy of 

 the human mind cannot be withstood, anil liy|)()- 

 thesis i)erforms a useful function in serving to 

 coordinate the observed phenomena of nature, 

 and in leading us to search for further evidence, 

 which shall serve as its confirmation, or perhaps 

 lead to its rejection in fa\()ur of truer \ie\\s. 

 The immense amorphous nebulae, of no regular 

 form, such as the great nebula of Orion, the nebula 

 round Eta Argus (now often called Eta Carinae), 

 the Omega nel^ula, the Trifid nebula in Sagittarius 

 (see Figure 441) and the America nebula (so-called 

 from a rough resemblance in its shape to that of North 

 America) (see Figure 442) may perhaps be regarded as 

 '■forming portions of the universal chaos in which 

 order has not yet been introduced." The annular 

 nebulae, planetary nebulae and special nebulae repre- 

 sent a later stage. Professor See suggests that such a 

 nebula as the King Nebula in Lyra (see Figure 4.59) 

 hasbeenformed by the union of two streams, indicated 

 by the blurred ends of their overlapping giving rise to 

 the hazy nebulosity at the e.xtremities of the ellipse. 

 The veil or " gauze over the hoop " perhaps due to 

 wastage from the latter by increasing, may gradually 

 cause it to assume the annular form, a more or less 

 uniform disc of light. The researches of Dr. Max 

 Wolf, of Heidelberg, have shown that at least four 

 different gases are present in this nebula, hydrogen, 

 helium and two other as yet unknown substances, 

 one of which may be identical with the " coronium " 

 of the Solar corona. Dr. F"ath, of the Mount Wilson 

 Solar Observatory, has recently examined the 

 question as to the true nature of the spectra given 

 by spiral nebulae generally. It had been generally 

 believed that these bodies usually gave a characterless 

 continuous spectrum unmarked by lines either bright 

 or dark, but the great faintncss of their light 



rcndircd very long ex))osures necessary to obtain 

 satisfactorv photographs of their spectra. Neverthe- 

 less such had been obtained, and the result showed 

 that " no spiral nrbiil.i investigated has a truly- 

 continuous spectrum." The |)rimary or fundamental 

 part appears to be continuous ; but it is interrupted 

 l>\- absorption lines, and in some cases we find bright 

 lines or bands. Thus, Professor See infers that this 

 indicates that these bodies, in addition to their 

 gaseous or ultra-gaseous matter, have an abundance 

 of moons and planets scattered throughout their mass; 

 their light may be " due to certain transformations of 

 energy, luminescent effects produced by electric 

 discharges in high vacua and light generated by the 

 im|3act of the various bodies contained within the 

 nel)ula."' He further supposes that these " moons " 

 arise from the precipitation of ions, and the con- 

 densation of cosmical dust on many centres, each 

 such centre being sufficiently distant from any other 

 to lie undisturbed by its attraction, .\fter a time in 

 the course of ages many of these " moons " coalesced, 

 and .so their number diminished : but the size of the 

 survivors correspondingly increased, impact and 

 collision continually going on. By the iinpa:ct of 

 numerous smaller bodies, he considers that the 

 characteristic lunar " craters " have gradually arisen, 

 a theorv of the origin of lunar surface phenomena 

 quite different from the usually accepted " volcanic " 

 theor\-, but one which is worthy of consideration 

 and is akin to the views of Humboldt. (Gilbert and 

 Proctor on the subject. 



If it be indeed the case that our own solar s\stem 

 has developed, not from a nebula of the kind 

 imagined b\- Laplace, but from a spiral nebula which 

 has gradually condensed, and the number of 

 independent members has been reduced by impact 

 and collision to a few whose paths have been 

 rendered nearls' circular by the long continued action 

 of the resisting medium, we may learn much of the 

 nature of both spiral nebulae and those of other kinds 

 from the stud\- of the system of w liich we form a part. 



CORRESPONDENCE. 



To tin- Editors of " Knowlkiige." 



Sn<s, — 1 should feci iiiiich obliged if any of your readers 

 would enlit'hteii iiic on the following point. 



The miiiiniiiin of the mean temperature curve for the year 

 does not, of course, occur exactly at the shortest day, but 

 some weeks after. There can be, unfortunately, no parallel 

 with regard to mean nightly minima, but we have the converse 

 case of the two hours lag of mean daily maxima after midday, 

 when the Sun is hottest, which involves the same principle, 

 viz. : that, owing to its accumulative properties with regard 

 to heat, the earth and hence the atmosphere, cannot respond at 

 once to a change of intensity in the Sun's radiation. This can 

 be actually observed on a clear, calm day with a suitably- 

 placed thermometer. Again, during the solar eclipse last 

 April, the minimum temperature occurred about twelve 

 minutes after the greatest phase. It was an ideal day 



in London and clear except ai tirst. Only shade temperatures, 

 of course, are referred to. My point is this: Cannot some 

 relation be found between these various lags? Irregularities 

 would surely be smoothed out in over fifty years' average. In 

 the case of the eclipse, I can only put forward that it happened 

 to be a clear day and as such would approach fairly near to 

 an average for similar conditions if it were possible to obtain 

 them. The rate of change of the flow of heat from the Sun is 

 known as regards its annual and diurnal change and, taking 

 the speed of eclipse into account, I take it the resultant rate 

 of change could be calculated for a period during the eclip.se. 

 I suppose the earth's properties as regards radiation and 

 absorption may be taken as constant in the three ca.ses. 



C.-\LOKIl-:. 

 2\0. .'XnEi.AinK RoAP. 



Sorrn Hanh'steap. 



