Miscellanies. 399 



constructed on this principle, was stated to have a far greater directive 

 energy than any instrument, of the nature of a compass, previously 

 constructed. Since that period Mr. Scoresby has been pursuing, as 

 opportunity offered, an extensive series of investigations on the sub- 

 ject; both as to the law of combination in steel plates and bars, and 

 as to the effect of temper, thickness, &c. on the aggregate power; 

 with the view of producing more powerful instruments for determin- 

 ing ihe delicate variations in, and the actual condition of, the earth's 

 magnetism ; a subject now engaging attention in some of the princi- 

 pal observatories in Europe. The results, which have been success- 

 ful beyond the objects originally contemplated, have been recently 

 communicated to the Institute of France. One of these results likely 

 to be of much importance in magnetical science, to which it is exten- 

 sively applicable, is that of producing permanent artificial magnets of 

 almost unlimited power. On the principle of construction of com- 

 pound magnets hitherto adopted, only a very limited number of bars 

 could be combined with advantage, in consequence of the great de- 

 terioration of power occasioned by the condition of violence. Mr. 

 Scoresby found, on combining very superior plates of tempered steel 

 of two feet in length and about g'^th of an inch in thickness, that the 

 first six plates received so much power that no additions, however 

 great the number, were capable of producing more, in the aggregate, 

 than about double that power. Aiming, however, to counteract the 

 tendency to such rapid deterioration, Mr. Scoresby made some mag- 

 netical combinations of -perfectly hard steel plates, (which he has a 

 ready method of magnetizing and testing,) by means of which an al- 

 most unlimited power can be obtained. Already this combination has 

 been carried, with no inconsiderable augmentation of the aggregate 

 energy, to the very last, to the extent of several dozens of hard plates, 

 15 inches in length, so as to produce, by such combination, a com- 

 pound magnet of very extraordinary power for its mass. The appli- 

 cation of this principle to apparatus for magnetic electricity will ob- 

 viously be of much advantage for compactness and power; whilst the 

 application of the discovery to variation needles, dipping needles, and, 

 probably, to sea compasses also, promises to be of ranch importance 

 in experimental science, as well as for practical and economical pur- 

 poses. Mr. Scoresby's investigations have also led to other practical 

 results, such as the means of testing most rigidly the quality and tem- 

 per of steel plates, and of bars intended for compound magnets on the 

 ordinary construction, by which the best plates can be selected and 

 the most powerful combinations may be obtained. — Lond. and Edin. 

 Phil. Mag., April, 1838. 



