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POPULAR SCIENCE REVIEW. 
the second, the least likely to prove instructive. We know as a matter of 
fact that, during the totality, and more especially at the beginning 
and end of totality, a variety of strangely changeful phenomena, result- 
ing from the varying illumination of our atmosphere by the promi- 
nences, sierra, and the really solar portion of the corona, may always he 
noted. It would he a problem of extreme difficulty to determine the precise 
way in which these variations are caused ; hut there can he very little 
question that they are chiefly due to the varying amount of illumination 
just referred to, and to the rapid changes of temperature resulting from the 
passage of the moon-shadow athwart the upper regions of the air. To pay 
special attention to such changes is a course admirably calculated, perhaps, 
to throw light on meteorological questions ; hut it does not seem to promise 
any new information respecting the real solar corona. The most valuable 
information respecting this remarkable appendage of our sun would un- 
questionably be gained if one observer, not suffering his attention to be dis- 
tracted by the wonderful spectacle produced by the changing illuminations 
of the upper air, could discriminate between the changeful phenomena of 
the eclipse and those features of the corona whose fixity pronounces them 
to be true solar phenomena. 
j Detection of the Annual Parallax of a Planetary Nebula. — Mr. Gill, of 
Aberdeen, well known as a careful observer, and as having executed some 
successful photographs of the moon, announced at the recent meeting of the 
British Association that he had detected a parallax of nearly two seconds in 
the case of the planetary nebula 37 H. iv., close by the pole of the ecliptic. 
He is desirous, however, of continuing his observations for yet another year 
before definitively announcing that the nebula has this large parallax. Should 
this result be confirmed, it would follow that this nebula is nearer to us than 
any of the fixed stars, or at least than any fixed star whose parallax has 
hitherto been measured. The result would be interesting, as confirming 
those doubts which have recently been expressed respecting the vast dis- 
tances at which nebula have been long supposed to lie. It must not be for- 
gotten, however, that Sir William Herschel, by whose observations these 
vast distances have been supposed to be established, was himself the first to 
express doubts on the subject. The planetary nebulae, in particular, were 
among the objects which he judged, during the latter part of his career as 
an observer, to be much nearer than he had imagined when he enunciated 
his earlier but better-known theories. It is somewhat singular that the 
particular nebula which has thus been the first to reward the search for 
nebular parallax, was the first nebula which Dr. Huggins found to be gaseous. 
A somewhat remarkable comment is reported to have been made by 
Professor Tait upon|Mr. Gill’s paper. That eminent mathematician re- 
marked, according to the report, that Mr. Gill’s observation, if established, 
would tend to overthrow the theory now universally accepted among astro- 
nomers respecting nebulae, — to wit, a that nebulae are the moving matter of 
stars ; showers of stones, Sir W. Thomson would call them, at inconceivably 
vast distances.” We had never heard that this theory had even been enun- 
ciated among astronomers, though we have had through our hands the pro- 
ceedings of all the principal astronomical societies of Europe and America, 
and all the most important treatises on astronomy which have been pub- 
