226 



NATURE 



\yan. 20, 1876 



tion, I devised the method described in Nature (vol. xii. p. 517), 

 showing that the polar and equatorial regions of the solar disc 

 transmit radiant heat of equal intensitv to^the earth, and that the 

 sun emits heat of equal energy in all directions. Adopting 

 Secchi's doctrine relating to the retardation suffered by calorific 

 rays in passing through atmospheres, viz., that the diminution 

 of energy is as the depth penetrated by the rays, it may also be 

 shown by an easy; calculation based on the result of our investi- 

 gations, that the absorption by the solar atmosphere cannot 



exceed one-seventh of the radiant energy emanating from the 

 photosphere. 



5. Concerning the plan ' re.sorted to by the Director of the 

 Roman Observatory, and others, of investigating the sun's image 

 instead of adopting the method of dinct observations, I will 

 merely observe that the information contained in the several 

 works of the Roman astrononi^r furnishes the best possible 

 guide in judging of the efficicy of image investigation. Let us 

 select his account of the investigations conducted between the 



19th and 23rd of March, 1852. Having pointed out that in 

 these experiments it was impossible to approach within a minute 

 of the edge of ihe sun, and that during a later observation — 

 date not mentioned — he had approached within a minute, the 

 investigator observes : "But at this extreme limit, even making 

 use of the most accurate means of observation, we fmd difficulties 

 which it is impossible to overcome completely." In addition to 

 this emphatic expression regarding the difficulties encountered, 

 the author adds : "Moreover, it is impossible to study the edge 

 alone, for the unavoidable motions of the image do not admit of 

 its being retained at exactly the same point of the pile ; we have 

 therefore been unable to push the exactness as far as we hoped ; 

 and we have discontinued the pursuit of these researches, although 

 the results obtained are quite interesting." (See revised edition of 



" Le Soleil," vol. i. p. 205.) It is needless to institute a com- 

 parison between a system of which its founder speaks so despond- 

 ingly, and one which enables us to push our investigations to the 

 extreme limit of the solar disc, admitting of entire zones being 

 viewed at once, instead of only small isolated spots. 



J. Ericsson 



The Glow-virorm in Scotland 



The Glow-worm is not uncommon on the Island of Cumbrae, 

 Buteshire. I have seen it there occasionally for the last thirty 

 years (see vol. xiii. pp. 188, 208). Daaid Robertson 



Millport, Island of Cumbrae, Jan. 18 



OUR ASTRONOMICAL COLUMN 



Star with Suspected Large Proper Motion. — 

 It would appear by a communication from Prof. Win- 

 necke, Director of the Imperial Observatory at Stras- 

 burg, that the large proper motion exhibited by a com- 

 parison of Argelander's positions of the ninth magnitude 

 star, No. 11237-8 of Oeltzen's catalogue (southern zones) 

 with Taylor's observations at Madras in 1838 or 1839, to 

 which reference was lately made in this column, does not 

 really exist, there being evidently an error in Taylor's 

 mean place for 1840 given at p. clxiii. of vol. v. of the 

 Madras Observations. Prof. Winnecke finds that the 

 differences of right ascension and declination between 

 this star and Oeltzen 11226, are sensibly the same as at 

 the. time of Argelander's observations (185 1), and the 

 latter star is known to have but very small, if any, proper 



motion. Taylor's star must therefore be struck off the 

 list of cases of great proper motion lately given. 



Atlas — 27/ Pleiadum. — A very interesting obser- 

 vation was made at Strasburg on the occasion of the 

 occultation of this star— a Struve's difficillima—on the 

 7th of the present month. As we recently stated, this 

 star does not appear to have been seen double since the 

 last Dorpat observation in 1830. On the 7th inst., how- 

 ever, Herr Hartwig observing at Strasburg with an excel- 

 lent Fraunhofer, of 42 lines aperture, power 159, remarked 

 that the star did not disappear instantaneously ; after the 

 principal mass of light had vanished there remained a 

 luminous point for about six-tenths of a second, a cir- 

 cumstance which favours the duplicity of the object, 

 notwithstanding the failure of recent efforts to divide it. 

 It brings to our recollection Burg's observation of the 



