AND MODE11N PHYSICH. 19 



published paper was communicated to the Royal 

 Society of Edinburgh on April 6th, 1846, when its 

 author was barely tifteea Its title is as follows: 

 " On the Description of Oval Curves and those having 

 a Plurality of Foci. By Mr. Clerk Maxwell, Junior. 

 With Remarks by Professor Forbes. Communicated 

 by Professor Forbes." 



The notice in his father's diary runs : " M. G [Ap., 

 1840.] Royal Society with Jas. Professor Forbes 

 gave acct. of James's Ovals. Met with very great 

 attention and approbation generally." 



This was the beginning of the lifelong friendship 

 between Maxwell and Forbes. 



The curves investigated by Maxwell have tho 

 property that tho sum found by adding to tho 

 distance of any point on tho curve from one focus 

 a constant multiple of tho distance of the same poiut 

 from a second focus is always constant 



The curves are of great importance in tho 

 theory of light, for if this constant factor ex- 

 presses the refractive index of any medium, then 

 light diverging from one focus without tho medium 

 and refracted at a surface bounding tho medium, and 

 having tho form of one of Maxwell's ovals, will be 

 refracted KO as to converge to tho second focus. 



About the same time ho was busy with some 

 investigations on the properties of jelly and gutta- 

 percha, which seem to have been suggested by Forbes* 

 " Theory of Glaciers." 



He failed to obtain the Mathematical Medal in 

 1846 possibly on account of these researches but 

 he continued at school till 1847, when ho left, being 

 11 2 



