Miscellanies. 177 



2. Electro-magnetic experiments. — Professor Moll, under date 

 of Utrecht, April 23, 1833, describes in the Bib. Univ. the result of 

 various experiments to ascertain how far he could diminish the gal- 

 vanic surfaces, and yet retain a considerable amount of magnetic pow- 

 er* His horse shoe was cylindrical, and when straight, measured 

 twenty four inches (English) in length ; diameter, two inches. It 

 weighed with its spirals twenty nine pounds. The iron was surround- 

 ed with an envelope of silk, and around this were rolled two spirals 

 (sinistrorsum) of soft iron of the diameter of T \ of an inch. These 

 spirals were not covered either with silk or any other substance. The 

 ends of these iron wires were soldered together, and communicated 

 by other wires with the simple galvanometric apparatus, consisting 

 always of a single element. The other extremities of these wires 

 were also soldered to the zinc and copper plates of the voltaic ele- 

 ment ; for his experience, (he observes,) and that of many others, 

 has taught him that a contact as intimate as possible between the spi- 

 rals and the zinc and copper of the battery, can alone secure com- 

 plete success. 



A little copper trough containing a plate of zinc of the surface (on 

 one side) of seven eighths of a square inch, gave the horse shoe, 

 (which had previously no sensible force,) a magnetic power which 

 sustained twelve pounds. In a second experiment the iron sustained 

 thirty nine pounds, and in a third forty eight pounds. Care was 

 taken to prove that the horse shoe, prior to each experiment, had no 

 sensible magnetic force. 



Prof. M. then took a piece of the smallest of the copper coin, and 



a piece of zinc of the same diameter, viz. about f of an inch. The 



horse shoe, with this, supported 6f ounces. He then used two of 

 these half cents, (as they are called in Holland,) united them by a 

 copper wire, and placed between them a disc of zinc of the same 

 diameter, and plunged the apparatus in a little wooden trough. The 



horse shoe then supported 14f ounces. With a two cent piece of 



copper, (I of an inch,) 2 lb. 5| oz. were sustained. With a twenty 

 franc gold piece, it supported 13f ounces. With a silver piece of 



half a franc value, % inch in diameter, the weight sustained was 13 



lbs. 3f oz. With a zinc plate of 4£ inches square, between two 

 plates of copper in a wooden trough, 80 lbs. were supported. With 

 a plate of zinc of 10£ inches square in a trough of copper, 224 lbs. 

 The acid menstruum was very strong. 



Vol. XX VI.— No. I. 23 



