76 JAMES CLERK MAXWELL. [CHAP. IV. 



M. 6. Eoyal Society with Jas. Professor Forbes gave 

 acct. of James's ovals. Met with very great attention and 

 approbation generally. 



The result of the attempt thus eagerly pursued, 

 as communicated by Professor Forbes that evening, 

 is embodied in the Proceedings of the Edinburgh 

 Royal Society, vol. ii. pp. 89-93. 



MONDAY, 6th April 1846. 



Sm THOMAS M. BRISBANE, Bart., President, in the Chair: 

 The following communications were read : 



1. On the Description of Oval Curves, and those having 

 a plurality of Foci. By Mr. CLERK MAXWELL, 

 junior, with Eemarks by Professor FORBES. Com- 

 municated by Professor FORBES. 



Mr. Clerk Maxwell ingeniously suggests the extension 

 of the common theory of the foci of conic sections to curves 

 of a higher degree of complication, in tjie following manner : 



1. As in the ellipse and hyperbola, any point in the 

 curve has the sum or difference of two lines drawn from two 

 points or foci = & constant quantity, so the author infers 

 that curves to a certain degree analogous may be described 

 and determined by the condition that the simple distance 

 from one focus, plus a multiple distance from the other, may 

 be = a constant quantity ; or more generally, m times the 

 one distance 4- n times the other = constant. 



2. The author devised a simple mechanical means, by 

 the wrapping of a thread round pins, for producing these 

 curves. See Figs. 1 and 2 (Plate 11). He then thought 

 of extending the principle to other curves, whose property 

 should be, that the sum of the simple or multiple distances 

 of any point of the curve from three or more points or foci, 

 should be = a constant quantity ; and this, too, he has 

 effected mechanically, by a very simple arrangement of a 



