22 



THE GUIDE TO NATURE 



FIG. 4. A RARE FORM OF AGATIZED CORAL OF INTERESTING FORMATION. 



slab of stone laid on it, in direct contact 

 with the sensitive film. A large parlor 

 match was then burned a short distance 

 above, and the shadow cast by the stone 

 impressed itself in the sensitive emulsion 

 of the plate. In all the illustrations the 

 detail in the original specimens is ren- 

 dered faithfully. [The author's illus- 

 trations have been enlarged for publi- 

 cation.] 



An Easy Experiment with Electricity. 



BY F. R. GORDON, YPSILANTI, MICH. 



An instructive experiment on the con- 

 duction of electricity by a liquid can be 

 performed wherever a commercial light- 

 ing circuit is within reach. Let us sup- 

 pose the voltage is 110, which is probably 

 the one which is most commonly used. It 

 may be either a direct or alternating cur- 

 rent. We shall also suppose that a common 

 16-candle-power lamp is at hand con- 

 nected with a few feet of double lamp 

 cord. The experiment is as follows : 



Switch off the current from the lamp 

 and cut one of the two cords. Cut off 

 the insulation for about an inch at each 

 of the two ends made by cutting the wire. 

 Place these two ends of wire down in a 

 tumbler of water, and make sure that 

 they do not touch each other. When you 

 have made everything ready, switch on 

 the current. The lamp will probably not 

 light up. If it glows at all, it will be but 

 faintly. Now drop into the tumbler, a 

 little at a time, a few grains of common 



salt, and stir carefully. As you stir the 

 liquid and the salt dissolves, the lamp will 

 glow more and more brightly until it 

 reaches pretty nearly its full brilliancy. 



The explanation of this phenomenon is 

 based upon the fact that electricity is car- 

 ried through a liquid by means of so- 

 called ions. There are so few ions in 

 water that it conducts very poorly ; but 

 when a little of the salt has dissolved, 

 some of the molecules of salt (which is a 

 compound of an element called sodium 

 and another element called chlorine) split 

 in two. This splitting apart gives rise to 

 ions of sodium and other ions of chlorine. 

 Hence as more and more of these ions are 

 produced in the water, the more rapidly 

 the current of electricity is carried from 

 one end of the wire to the other. Since 

 all this current has to pass through the 

 lamp, the filament of carbon is heated 

 hotter and thus glows more brightly. 



No doubt my life as a farm boy 

 has had much to do with my subse- 

 quent love of nature, and my feeling 

 of kinship with all rural things. I feel 

 at home with them ; they are bone of 

 my bone and flesh of my flesh. It 

 seems to me a man who was not born 

 and reared in the country can hardly 

 get Nature into his blood, and estab- 

 lish such intimate and affectionate re- 

 lations with her, as can the born coun- 

 tryman. — "Our Friend John Bur- 

 roughs," by Clara Barrus. > 



