372 



KNOWLEDGE 



[Nov. ;?, 1882. 



I have called "the thermal continuity of liquids and from as many correspondents. None of these (and somo 

 rapours." It is, I think, the strongest illustration liitlicrto score of others, who have descriSed without picturing the 



adduced of the conservation of molecular action. 

 mail's Matjaxiii': 



THE COMET. 

 By R A. Proctor. 



(Cond'niifd from page 855.) 



THE illustrations which we give this week speak for 

 themselves, and will serve better than any verbal 

 description to show what the Comet is doing at present, 

 where it is goinjr. and what it looked like when last well 

 seen in this country. 



In the tirst place, we give a map (Fig. 1) showing the 

 course of the Comet among the stars during the present 

 month. 



The map has been formed from a section of one of the 

 twelve maps of my " Library Star Atlas." The direction 

 of the tail is such as to correspond to the direction of a 

 great circle towards the point on the star-sphere opposite 

 to the position of the sun's centre. 



But tliis map, being taken from a star atlas, is not cal- 

 culate<l to show the position which tlie comet will have 

 upon the fki/, as distinguished from the star-sphere, espe- 

 cially as the region athwart which the comt-t is at present 

 travflling is not rich in conspicuous stars. (The star « 

 Hydr.T, the neare.st tliird magnitude star, see Figs. 2 and 

 3, is called Alphard, or the solitary one.) 



Vi'e might rt-fi-r those of our readers who possess 

 Parts IV. and V., or the numbers for Feb. .1 and March 3 

 (14 and It^) to tlie star-majis corresponding to the hours 

 between which the comet will be best seen in November ; 

 for those maps, which are for 10 p.m. on Feb. C and 

 March t* respectively, show the aspect of the lieavens 

 two hours later, or at midnight on Jan. 7 and Feb. C 

 respectively ; two hours later still on Dec. 7 and Jan. 7 

 respectively ; two hours later, or at 4 a.m. on Nov. G and 

 Dec. 7 rwpectively ; and thus the second of tliem (that 

 given in No. IS) shows the aspect of the heavens at a.m. 

 on Nov. C. We have them in the maps for February and 

 March, at 10 p.ni , the aspect of the heavens at 4 a.m., 

 and at << a.m. on Nov. : and readers who possess these 

 maps can at once turn to them to see whereabouts tlie stars 

 shown in Fig. 1 are at these hours ; wlience, of course, 

 their position at any intervening time can be at once in- 

 ferred, the motion being slight in the interval. On Nov. 

 1 1 the maps show the aspect of the heavens from .3.4.5 a.m. 

 to r>A'> a.rn. ; and so on, earlier liy a quarter of an hour for 

 each four days (al)Out) ; until on Dec. C we have the second 

 map fchowing the heavens for 4 a.m., but still serving to 

 indicate the aspect of the star sphere to later hours, because 

 the diurnal motion of the heavens in the part where the 

 comet is, lies in the morning hours nearly parallel to the 

 horizon. 



But, as many of our present readers do not'possess thete 

 i-atVut star maps, we liave thought it well to give sections, 

 showing those parts of tlie sky where the comet is in the 

 early morning hours. All that we have just said applies 

 to Figs. 2 and .3.* 



In fig. 4 I give a picture of the comet formed after 

 careful study of seventeen pictures which have reached me 



• I may notice in pa«»ing that poMi'ljIy thio illn^tratiro cane irny 

 give many a U-ttt-r UU-n of the way in whicli the monllily mnpH nro 

 meant to >«• n'c4, than thfy have hitherto ha-l. In rc-piil)lifiliiri(f 

 them, I am a>lding a tahlo showing the times all IhrowjU the vi'jht 

 at which the mapa can be used. 



comet) seern to have noticed the marked form of 

 fork of the tail, as described by Major John 



I 



