PLYMOUTH INSTITUTION. l63 



has been evolved by the influence of magnetic action, which is the 

 converse of Orested's discovery. Mr. Harris here narrated Dr. 

 Faraday^s experiments, in illustration of the above discoveries, and 

 proceeded to state that Dr. Faraday showed that electrical currents 

 are induced in every mass of metal, moving under the influence of 

 magnets, which currents are excited in a direction transversely to the 

 direction of motion ; he has on this principle succeeded in construct- 

 ing electrical machines of a new kind, by revolving copper plates in 

 contact with the poles of a magnet. Dr. Faraday has also given an 

 account of magno-electric induction, derived from the influence of 

 the Earth^s magnetic action, another step of magnitude in these 

 sciences. Mr. Harris considered the papers published by Dr. 

 Faraday, containing a detailed account of the above discoveries, as 

 ranking among the first productions of the day, and being highly 

 creditable to British science. Before quitting this part of his sub- 

 ject, Mr. H. mentioned that in Dr. Faraday's last paper he endea- 

 vours to show that all the different species of electrical action are 

 derivable from the same source, and he also states that he has arri- 

 ved at some new views in electro-chemistry which promise to extend 

 greatly the operation of the Voltaic pile in the disunion of bodies 

 considered elementary. 



In the department of Meteorology some useful results have been 

 arrived at by Professor Daniell and Mr. Hudson ; the former found 

 that the water barometer, in the hall of the Royal Society, is always 

 in advance of the mercurial one, which Mr. Hudson shows to be an 

 hour in time ; he also shows that a standard barometer of large bore 

 precedes a mountain one of .15 of an inch by about the same period, 

 and further showed by means of tubes of different sizes, inserted in 

 a common cistern, that the larger are always in advance of the 

 smaller ones. 



In noticing the last number of the Philosophical Transactions, 

 Mr. Harris observed, that Mr. Barlow was still engaged in the im- 

 provement of refracting telescopes, by the use of fluid lenses : by this 

 method telescopes of an extraordinary power may soon be obtained. 



Mr. Whewell has a paper in the same publication on the tides, 

 in which it seems to be his object to arrive at an approxima- 

 tion to a map of the tides, by drawing lines, called Cotidal LineSf 

 through all the points in the world at which it is high water at the 

 same instant of time. It was stated that this paper contained much 

 information on the effect which large and small masses of land have 

 in varying the action of the regular tide wave, as well as considera- 

 tions of the effect of arms of the sea, bays, shallow and deep places, • 



