ANNALS OF THE ACADEMY 83 
present case, this labor has been greatly simplified by the recent publication by Sir 
William and Lady Huggins, of an Atlas of Representative Spectra from wave 
length 4,870 to 3,300, together with a discussion of the evolutional order of the 
stars, and the interpretation of their spectra, preceded by a short history of the 
Observatory and its work. This monumental volume not only furnishes a state- 
ment of the various publications of the authors, but exhibits the relation of the 
various investigations undertaken much better than could readily be done by 
another. From this it appears that the work began in 1856 with a 5-inch Dolland 
equatorial, which was replaced two years later by an excellent 8-inch Clark tele- 
scope. In 1870 this was again replaced by a 15-inch achromatic and an 18-inch 
reflector. In 1858 Sir William, then Mr. Huggins, undertook with Dr. Miller 
the visual study of stellar spectra. This work was continued until 1864, and the 
results were communicated to the Royal Society. Soon after this, on August 29, 
1864, Sir William made one of the great discoveries in astrophysics. He found 
that the spectrum of the planetary nebula in Draco, N. G. C. 6543, had a mono- 
chromatic spectrum. 
“Tt has heretofore been supposed that all nebulz might consist of distant stars 
and could be resolved into their components by a telescope of sufficient power. 
This theory was at once disposed of, and it appeared that of 60 of the brighter 
nebulz and clusters about one-third were of this gaseous character. In 1866 
the observations of the new star in Corona gave the first clew to the cause of 
these remarkable objects. In 1868 Sir William was able to announce the first 
step in an investigation which in recent years has become one of the most impor- 
tant in astrophysics. The hydrogen lines in the brightest stars showed a slight 
displacement, from which the motion of these bodies in the line of sight may be 
determined. The accurate measurement of this quantity is now occupying a 
large part of the time of the greatest telescopes in the world. It is leading to 
unexpected results, which throw important light on the formation of the universe. 
The fact that these displacements are wholly independent of the distance of the 
source of light gives an opportunity to study problems for which ordinary visual 
methods fail entirely. About this time, also, a study of comets showed that their 
spectra closely resembled that of olefiant gas. A proposal of great scientific 
importance was a method of observing the solar protuberances in the uneclipsed 
sun. This method was devised independently by Mr. Lockyer. It is now 
claimed that these remarkable phenomena can be better seen any clear day at a 
fixed observatory than with portable instruments during a total solar eclipse. In 
1876 the study of the spectra of the stars by means of photography, which had 
been attempted without attaining satisfactory results in 1863, was undertaken. 
Among the results published four years later, one of the most important was the 
discovery of the wonderful series of lines due to hydrogen. Similar series of lines 
are now found to exist in the spectra of many other terrestrial elements, and form 
the basis of the spectroscopic relation of these substances with one another. 
