No. 112:] • 253 



that what we call the polar star, is made up of two stars ; that 

 the pleiades are a collection ; and that those nebulous patches 

 which illuminate the broad belt of heaven can be resolved into 

 innumerable worlds, too great in numb( r ibr the hunu.n mind 

 to grasp the idea. I believe that T have some comprehension of 

 measurement, geoerally, but I coniess that the only way I can gain 

 any idea of the immense distance, the vast space of those stars 

 from us, is by calling to mind the fact, that light which travels at 

 the rate of many thousand miles an hour, is three jnilliohs of years 

 coming from the neaiest of th( ni to us. All these wonderful 

 things, has the telescope made known to us. Bu^ woi^derlul and 

 magnificent as they are, they must yield to what the microscope 

 has accomplished. ^Yhen we say -'the microscope," we mean not a 

 microscope, but the microscope, the reason for which will soon be 

 apparent. 



A ray of light passii}g through the glass, water or any medi- 

 um differing in density from the air, suffers what we call refrac- 

 tion ; that is, it is bent from its course. It is again bent from 

 the second course, upon its emerging from that medium into the 

 air upon tlie other side, and preserves its parallelism. It passes 

 on in a line parallel to that hy which it entered the refracting 

 medium. Take for instance common glass, and we have an ex- 

 ample of this elfect. (The Professor drew upon the black board 

 a figure of a double convex lens, and made apparent to the class, 

 by practical demonstration, what he intended to convey.) 



But let us lay aside the comuKm glass, and taking aprism,sul- 

 fer a ray of light to pass t^irough it, we finrl that ray, white 01 i- 

 ginally, is separated into seven rays, of ditferent colors, and those 

 seven are the 2)rimary colors which we find in the rainbow. And 

 here is something we have to contend with. Glass will always 

 have a tendency to decompo.^e light, and resolve it into these con- 

 stituent parts, and hence when we have our instruments construc- 

 ted of common glass, they are good for nothing. All things viewed 

 through these aie tinged with a halo of the j>rismatic colors, all 

 is confused and indistinct. 



But lie who from the beginning of time has never failed in the 

 construction of anything, lias given to man and animals a perlect 



