658 THE POPULAR SCIENCE MONTHLY. 



the ethereal waves of still more rapid undulations and lesser length 

 furnish the actinic force of light. And if the mathematical deductions 

 of such as Maxwell and Boltzmann, together with the refined research- 

 es of many others in this border-land of science, are not at fault, we 

 would not be surprised if, at some early day, the solution of the phe- 

 nomena of electricity should be found in some way connected with 

 ethereal vibrations, infinitely more rapid and minute than those which 

 produce the actinism of the ultra-violet spectrum. The difficulties at- 

 tending the solution of this problem maybe moi-e fully comprehended 

 when we recollect that, in dealing with vibrations more rapid than 

 those bordering the visible spectrum, we are leaving regions where 

 the undulations comprise nearly one thousand million of millions in a 

 second of time, only to be confronted with others of infinitely greater 

 rapidity. 



These ethereal and molecular actions are going on eternally about 

 us. The photographer's sensitized plate may receive an image that 

 maps out the constellations, or, through the prism of the spectroscope 

 in lines of light, we may read of the constituents of the nebulae, and 

 thus upon the waves of ether do we hold communion across the uni- 

 verse by that ethereal chain of motion which binds us to the stars ! 



-- 



SIMPLE EXPERIMENTS IN OPTICS. 



By ELIZA A. YOUMANS. 



THE little work of Mayer and Barnard, designed to introduce be- 

 ginners to the experimental study of optics, is so much needed, 

 so skillfully done, and may be so helpful to teachers and students of 

 all asres, that it is desirable to ofier a few illustrations of the method 

 of experiment adopted, and to point out some of the cheap and simple 

 ways which Prof. Mayer has hit upon for exemplifying and proving 

 optical phenomena. We shall make free use of his text as well as his 

 cuts in the present article. Fig. 1, for example, represents the ar- 

 rangement adopted to prove that light moves in straight lines. He 

 first gets three little blocks, two or three inches square ; then three 

 slips of pine, three inches by four and one-eighth of an inch thick ; 

 and then three postal-cards, through which a small apertui-e is to be 

 made. The authors say: "Just here we need a tool for making small 

 holes and doing other work in these experiments ; and we push, with 

 a pair of pliers, a cambric needle into the end of a wooden pen-holder 

 or other slender stick, putting the eye-end into the wood, and thus 

 making a needle-pointed awl." This is an excellent little contrivance, 

 and we suggest to the pupil to make a set of them with difierent- 

 sized needles, which he will find very useful. Now, lay^the postal- 



