RECENT WONDERS OF ELECTRICITY. 669 



were this isthmus to be submerged, the great body of heated water, 

 that at present finds its way north through the Straits of Florida, 

 might flow directly into the Pacific Ocean. There is no evidence, how- 

 ever, to show that the barrier of Darien has been thus submerged with- 

 in any recent geological period, and consequently the great changes of 

 climate referred to above could not have been brought about in this 

 way. They were most probably induced, as Dr. Croll has shown, by 

 a remarkable series of physical mutations, which accompanied and 

 were caused by the last great increase in the eccentricity of the earth's 

 orbit. As the next period of high eccentricity will not occur for 

 many thousands of years, we need have no apprehension that we shall 

 be deprived of the genial influence of our friendly Gulf Stream in the 

 immediate future. And when we reflect upon the magnitude of the 

 submergence of Central America which would be required to divert 

 that stream into the Pacific, Ave may be equally reassured that we are 

 not likely to suffer from its loss in our day, for, before it could be 

 sensibly diminished in volume by this means, the Isthmus of Darien 

 would need to be sunk to a depth of not less than 800 feet, and per- 

 haps even 1,000 feet. We may therefore contemplate with perfect 

 composure the formation of any number of canals across that isthmus. 

 The great work of the famous French engineer will have as much 

 effect upon the Gulf Stream and the climate of North western Europe 

 as the emptying of a teapotful of boiling water into the Arctic Ocean 

 would have in raising the annual temperature in Greenland. British 

 Trade Journal. 



EECENT WONDEES OF ELECTRICITY.* 



Br W. H. PEEECE, F. E. S. 



I OUGHT to commence, if I carried out the customary practice, by 

 addressing the audience as ladies and gentlemen, but to-night I 

 much prefer commencing with boys and girls, because the two lectures 

 that I am about to deliver to you are really intended to be addressed 

 to the youngest members of the society. I would first direct your 

 attention to the fact that this hall is illuminated by electricity, and, 

 although I do not intend in any way to refer to the electric light 

 to-night, it is my intention, step by step, to lead you up to it, so that, 

 when we part this day week, I hope and trust to be able to let you de- 

 part with a thorough and complete knowledge how electricity works 

 and how it produces these marvelous effects. To accomplish this ob- 

 ject there are two things most essential : the first is, that I, your lect- 

 urer, should be perfectly clear in my definitions, and simple in the 



* Lecture delivered before the Society of Arts, December 28, 1881, and reprinted 

 from the journal of the society. 



