322 
SECOND REPORT-18.32. 
and in the refracting body*; but this only removes the diffi¬ 
culty a step further, and leaves the mind impressed with the 
conviction that the production of such a system of defective 
rays by the action of a gaseous medium presents a formidable 
difficulty to the undulatory theory. 
But whatever hypothesis be destined to embrace and explain 
this class of phenomena, the fact which I have mentioned opens 
an extensive field of inquiry. By the aid of the gaseous ab¬ 
sorbent, we may study with the minutest accuracy the action of 
the elements of material bodies in all their variety of combina¬ 
tions, upon definite and easily recognised rays of light, and we 
may discover curious analogies between their affinities and those 
which produce the fixed lines in the spectra of the stars. The 
apparatus, however, which is requisite to carry on such inqui¬ 
ries with success cannot be procured by individuals, and cannot 
even be used in ordinary apartments. Lenses of large diameter, 
accurate heliostates, and telescopes of large aperture are abso¬ 
lutely necessary for this purpose ; but with such auxiliaries it 
would be easy to construct optical combinations, by which the 
defective rays in the spectra of all the fixed stars down to the 
tenth magnitude might be observed, and by which we might 
study the effects of the very combustion which lights up the 
suns of other systems. 
Report on the Recent Progress and Present State of Minera¬ 
logy. By W. Whewell, M.A., Fellow and Tutor of Trinity 
College , and late Professor of Mineralogy in the University 
of Cambridge. 
Mineralogy may be said, in a certain sense, to have continued 
to be a popular science ever since the time when Werner and 
Haiiy inspired their pupils with so much enthusiasm and acti¬ 
vity. During the course of the subsequent years very many 
persons have employed themselves in making collections of mi¬ 
nerals, public and private; in arranging and naming the speci¬ 
mens; in referring their forms and characters to the types of ac¬ 
knowledged species. In England, as well as elsewhere, our best 
chemists have frequently analysed mineral specimens; and we 
have had here persons at least as skilful as have appeared in 
any other country, who have disentangled the crystalline forms 
and examined the optical properties of minerals, and have thus 
* This supposition is countenanced by the remarkable fact which I have 
placed beyond a doubt,—that there are in different parts of the spectrum two 
or more sets of rays which have the samerefrangibility, or which undulate with 
exactly the same velocity; and yet one of these sets of rays will freely permeate 
certain transparent bodies, or excite undulations in its aether, while the other sets 
are absorbed, or are incapable of propagating undulations through the body. 
