364 Researches in Magnetic Electricity. 



stone, merely from its external characters. All the rocks in Ohio, 

 except the tertiary and recent deposits, belong, in my opinion, to 

 the transition of Buckland, which would include the coal meas- 

 ures and the mountain limestone, the oldest visible rock in Ohio. 

 Those rocks which the Doctor has mistaken for new red sand- 

 stone belong to the sandstone of the coal measures. I think I re- 

 mark in my review, (I have not a copy,) that I regard those rocks 

 in the eastern part of the State, as the most recent, aside from the 

 superficial deposits, since the dip is E. S. E., and unbroken. At 

 Wheeling, two beds of coal crop out, which extend into Ohio. 

 For these reasons, I think that neither the new red sandstone, 

 nor the lias, nor the oolite, is to be found in Ohio. I was desirous 

 to discuss this point, as the impression has gone abroad, that the 

 new red sandstone is found here. 



Art. XL — Researches in Magnetic Electricity and new Mag- 

 netic Electrical Instruments ; by Chables G. Page, M. D. 



1. Compound Electro-Magnets for the Magnetic Electrical 

 spark, shock aiid decomposition.- — In the last number of this Jour- 

 nal, I announced this new form of magnet, as decidedly superior 

 to the common solid electro-magnet, for exhibiting magnetic elec- 

 trical phenomena. I have since performed a variety of experi- 

 ments, with reference to the best mode of constructing these mag- 

 nets, and arrived at some beautiful results and important conclu- 

 sions. I find that the magnet made of flat plates of thin hoop 

 iron, answers best for lifting power and sparks ; but those made of 

 fine annealed iron wire, answer nearly as well, and (for reasons, by 

 and by to be mentioned) will in some cases be found preferable to 

 the flat bars. Sixteen magnets were made of soft iron wire, in bun- 

 dles of various lengths and diameters. Thirteen were made of No. 

 26 wire, two of No. 16, and one of No. 8. For lengths within ten 

 inches and diameters within one inch, the very fine wires answer 

 best. But for longer and larger magnets than these, the larger 

 iron wires answer equally well. Each of these magnets were 

 tried with one, two, and three coils of No. 16, copper wire, (wound 

 each the whole length of the bars and superposed by a single 



