Ixxiv PROCEEDINGS OF THE GEOLQGICAL SOCIETY. 



Formations/ in which he discusses the opinions of the most eminent 

 of his predecessors, and maintains, with Humboldt and Von Buch, 

 that the two great forces, aqueous and igneous, have acted simul- 

 taneously throughout the world's history, so that in every formation 

 principally resulting from aqueous action or deposition there ought 

 to be found evidences or results of igneous action also. He also 

 greatly extends in this treatise the doctrine of the inflowing of fresh 

 water, when he observes that " it is from want of reflection that 

 fluvio-marine formations have been considered only local accidents of 

 an estuary or gulf, as it may be aflirmed that, in certain seas bounded 

 by vast continents, the inflowing fresh waters produce more efl'ect on 

 the marine deposits than the sea-waters," and in support of this 

 opinion adduces the fact, that plants brought by river action into the 

 Gulf of Mexico have been carried to the coasts of Iceland and Spitz- 

 bergen. In fact, after discussing the various efl'ects produced simul- 

 taneously in the present seas, and showing that at every preceding 

 epoch similar variations in the effects produced at different localities 

 were also simultaneous, he gives the characteristics for distinguish- 

 ing the fluvio-marine from the purely marine formations of all ages ; 

 and in respect to the synchronism of aqueous and igneous forces, he 

 says, " the results of the study of actual phsenomena when applied 

 to the explanation of ancient phsenomena have demonstrated, as an 

 incontrovertible truth, the synchronic action of the two principal 

 causes, Plutonic and Neptunian, during all ages." 



The peculiar care bestowed upon his works by M. Prevost, and 

 his nervous dread of publishing anything not quite complete in his 

 own estimation, have been thus recorded by M. Deshayes : — 



" The works of Constant Prevost are numerous, and all of them 

 of incontrovertible merit ; among them there are some which, by their 

 importance, place their author in the most elevated rank among 

 savans : we ought to have a greater number ; but he was one of those 

 who blamed too much that precipitation which often induces persons 

 to publish imperfect works. After having accumulated immense ma- 

 terials, he still retarded the moment of producing them, from the 

 fear of being yet incomplete. Looking upon science with an eye too 

 keen not to observe its defects and gaps, he still preserved the hope 

 of perfection in time, and this was the reason he so constantly delayed 

 the publication of his most important works." 



On the 29th of April, 1836, M. Prevost was appointed Chevalier 

 de la Legion d'Honneur, and was subsequently raised to a higher grade 

 in that order. In February 1848, he was chosen a Member of the 

 Academy of Sciences with a large majority. He died on the 16th of 

 August, 1856, most deeply and sincerely lamented by all the great 

 men with whom he had been so long and so closely associated ; for, 

 though he was, like Blainville, a warm disputant, whether maintain- 

 ing his own opinions or attacking what he deemed the errors of 

 others, he never allowed the heat of argument to degenerate into 

 personal acrimony, but was at once candid and conciliatory to his 

 opponents. He was generous in every respect, having liberally con- 

 tributed to the Paris Museum his large collections, especially those 



