ASTRONOMY. 397 



solar surface has everywhere the same constitution.'" {Nature^ Feb- 

 ruary 4, 1886.) 



Sun-spot maximum. — The exact epoch of the last sun-spot maximum, 

 which for some time remained in uncertainty, has been placed by Wolf 

 at 1883-9, and his result has been confirmed* by the observations of 

 the past year. The previous maximum was well marked at 1870-6 and 

 with the 11-year period (more exactly 11-1 years) the next was expected 

 at 1881-7 or the beginning- of 1882 ; and in fact in April, 1882, a " false" 

 maximum did occur, but with the finally established maximum at 1883-9 

 we have a retardation of about two years. The interval from the pre- 

 ceding maximum is therefore 13.3 years, and from the preceding mini- 

 mum of 1879-0, 4-9 years. It is quite remarkable also that the varia- 

 tions of the magnetic needle have shown a similar anomalous fluctua- 

 tion. 



The Solar Coronal {a lecture delivered at the Royal Institution, by Dr. 

 Huggins, February 20, 1884). — "After mentioning the various hypotheses 

 concerning the nature of the corona (a gaseous atmosphere, tine par- 

 ticles ejected by the sun and in motion around the sun caused by several 

 forces, one of them being perhaps the repulsive force observed in the 

 case of comets, a center of meteoric streams, etc.). Dr. Huggins speaks 

 of Dr. Hastings's new theory, according to which the corona is not a 

 reality but simply a phenomenon caused by diffraction. Without dwell- 

 ing upon the proof of its reality furnished by photographs made when 

 there was no eclipse, and consequently no intervention of the moon, Mr. 

 Huggins finds that the analysis of the spectra of different parts of the 

 corona and the peculiar structure seen in the photographs taken during 

 eclipses contradict Dr. Hastings's theory. If Dr. Hastings's theory were 

 correct the corona would of necessity change during the course of the 

 eclipse and the photographs reveal no change. M. Janssen says : ' Les 

 formes de la couronne ont 6t6 absolument fixes pendant toute la duree 

 de la totality.' 



" The sun is doubtless surrounded by a gaseous atmosphere of a cer- 

 tain extent, but there are a number of reasons why the corona should 

 not be regarded as a prolongation of this atmosphere. A gas even a 

 hundred or a thousand times lighter than hydrogen at the height of the 

 corona would, at the sun's surface, be heavier than metals, — a state of 

 things which spectroscopic and other observations show cannot be the 

 true one. The corona does not show either that rapid condensation 

 towards the sun which an atmosphere would show, especially if we take 

 into account the effect of perspective in increasing the brightness of 

 the lower parts of the corona. Moreover, comets have been known to 

 pass through the upper part of the corona without losing either matter 

 or velocity. 



* Sur le statistique solaire de l'ann<5e 1885. Compt. Eend. 10-2 : 161. 

 t See The Observatory, vol. 8, p. 153. 



