134 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



a telescope. He introduces between the ordinary eye-piece 

 and the eye of the observer a small tube containing a cylin- 

 drical convex lens of about four inches' focal length, for which 

 lens, under different circumstances, we may substitute other 

 lenses of different lengths of focus. "Within the tube contain- 

 ing this lens, and between it and the eye, there is inserted a 

 second tube holding an ordinary direct-vision prism, such as 

 is made by Browning. The intensity of light in this ocular 

 spectroscope is so considerable that in combination with a 

 small portable telescope of one and a half inches' aperture it 

 shows distinctly the lines of stars of the first magnitude, and 

 of the crescent of Venus. It is peculiarly applicable to the 

 systematic observation of star spectra in which the main ob- 

 ject is to ascertain the typical constitution of the spectra. 

 1A 9 XL VIII., 156. 



THE BEGINNINGS OF SPECTRUM ANALYSIS. 



According to Lockyer, the distinguished Swedish philos- 

 opher Angstrom, whose untimely death in June, 1874, was 

 at the time chronicled by us, will be forever considered as 

 the founder of spectrum analysis, although unfortunately the 

 obstacles opposed by the language in which his first treatise 

 was written, and by distance from the scenes of his investiga- 

 tions, for three years prevented even its existence from being 

 known to the scientific world at large. His work, " Optiska 

 Undersokningar," published at Stockholm in 1853, was the 

 first publication in which use was made of a principle already 

 propounded by Euler, viz., that the particles of a body in con- 

 sequence of resonance absorb principally those sethereal un- 

 dulating motions which are impressed upon them. He also 

 endeavored to show that a body heated until it glows emits 

 the same kind of licrht and heat which it absorbs under 

 other circumstances ; he further stated that in many cases 

 the Fraunhofer lines are the inversion of the bright lines 

 which are observed in the spectra of various metals in the 

 galvanic arch. 12 A, X., 377. 



SPECTRA OF CERTAIN RARER METALS. 



Professor Thalen has published the result of an investiga- 

 tion into the spectra of the rarer metals yttrium, erbium, 

 didymium, and lanthanium. He has operated with large 



