respect mg Eduard Hiisscy Del aval. 31 



specting Mr-Delaval's " Recherches experimentales snr le Cause 

 des Changemcuts de Couleur dans les Corps opa(mes nuturella- 

 ment Co'.orees." Le Professeur Castelloii thus observes, " C'e^C 

 done a I'expcrieuce qii'il faut recourir si Ton vent connoitre !o« 

 causes des plu'nomenes de phvsique. C'est le nic'thode dont 

 Bacon a si bien trace la theorie et dont Galileo ct Newton ont 

 si bien montre la prati(|ue. C'est le mt'thode que M. Delaval, 

 Membre de la Societe Royal de Londres, et mon confrere a 

 Get egard, a exacteinent suivie dans le Mcmoire qu'il m'a fait 

 I'honneur de ni'adresser aftn que je pr(iseiitasse a cette illustre 

 assenibk'e. Je le crois digne de son attention, et je vais le 

 conimettre a son jugement ; j'ajouterai seuleinent que j'ai 

 r^pete avec le succes le plus heureux plusieurs experiences con- 

 tinues dans cet (;crit." 



Mr. Delaval's conqjany was much courted by persons of genius ; 

 and besides tlie other gentlemen whose names have been already 

 mentioned, he was intimate with Dr. Lewis, Dr. Ingenhouz, 

 Mr. Magellan, Mr. Kirwan, Mr. Cavallo, and most of the men 

 of science of his time ; though he visited little, his house was 

 always open to men of al)ilities. He was ever ready to give 

 information and elucidate it by facts in their presence, and iu 

 the accuracy of his experiments no man was his superior. No 

 arts were made use of by him to trumpet forth his publications, 

 Init they were left to stand or fall by the test of experiment. 

 The Royal Societies of Upsal and Gottingen, tlje Institute of 

 Bologna, and the Literarv and Philosophical Society of Man- 

 chester, unsolicited iurolled him amongst their members. 



It may be necessary to note that Dr. Bancroft, in his publica- 

 tions intitled. Experimental Rcserches concerning the Philosophy 

 of Colours, has differed greatly in opinion with Sir Isaac New- 

 ton, and Mr. Delaval. Dr. Bancroft, in page 27, of the lirst 

 edition of his work, makes the following remark, after long cii- 

 ticisms on Mr. Delaval's publications. *' I also think it may be 

 deemed a matter of excuse and consolation that he has only 

 erred with Newton." It seems extraordinary after this asser- 

 tion, that Dr. Bancroft, in his late publication, in two volumes, 

 octavo, has so jjuzzled the subject, tliat in the Monthly Review 

 enlarged, for Sej)tember last, it appears that the Reviewers havtt 

 concluded that Sir Isaac New^tou and Mr. Delaval differed in 

 opinion. This is not the first time that Dr. Bancroft has be>e!i 

 unfortunate in his explanations, as may be seen in Dr. Ro))eit 

 Jackson's Letters to the Connnissioners of Military Inquiry, 

 page 5, where Dr. Jackson, in his Answer, saith ; " Me (Dr. 

 Bancroft) has attacked my writings, and in doing this he has 

 ffo mixed and garbled my words, so perplexed and pcrvcited my 



meaning: 



