510 SIMSON. 



omnimodo aggressus,"*) to the drawing a straight line 

 through four lines given by position, and which shall 

 be cut by them in three segments having given ratios 

 to each other. Now his solution of this problem, the 

 corollary to the twenty-seventh lemma of the first 

 book, has a porismatic case, that is, a case in which 

 any line that can be drawn through the given lines 

 will be cut by them in the same proportions, like the 

 lines drawn through three harmonicals in the porism 

 already given of the harmonical curve. To this Newton 

 had not adverted, nor to the unfortunate circumstance 

 that the case of comets is actually the case in which 

 the problem thus becomes capable of an infinite number 

 of solutions. The error was only discovered after 

 1739, when it was found that the comet of that year 

 was thrown on the wrong side of the sun by the 

 Newtonian method. This enormous discrepancy of 

 the theory with observation, led to a full consideration 

 of the subject, and to a discovery of the porismatic case. 

 When the studies of a philosopher, and especially 

 of a mathematician, have been described, his discoveries 

 recorded, and his writings considered, his history 

 has been written. His private life is generally un- 

 varied, filled with speculative inquiry, amused by scien- 

 tific reading, variegated only by philosophic conversa- 

 tion, unless when its repose is broken by controversy, 

 an incident scarcely possible in the story of mathe- 

 maticians. Dr. Simson loved to amuse his leisure 

 hours, and unbend his mind in the relaxation of so- 

 ciety ; and from the simplicity of his manners and the 



* Principia, lib. iii. prop. xli. 



