MAESILLI. BALDASAEI. SOLDAKI. 33 



assembled Academicians of Cremona a spirited exposition of 

 his theory. It may be stated as a farther and singular coin- 

 cidence, that as we owe to Professor Playfair, in later times, 

 the idea of a destructive and conservative power in nature, 

 which form a counterbalance to each other ; Generelli con- 

 cludes with enforcing the same principle, and contends that 

 Providence has constantly raised from the deep fresh moun- 

 tains to supply the disintegration of others, a fact, lie adds, 

 which satisfactorily accounts for the number of Crustacea and 

 other marine objects now found in many mountains. 



MAESILLI (1740) pointed out the very important truth 

 that fossil shells are not distributed at random,' but in certain 

 associations of genera, a fact which, somewhat later (1750), 

 was more fully established by DONATI. TAEGIONI (1754) 

 proved that the elephants whose remains were abundantly 

 discovered in various parts of Italy, once existed on the 

 strata from which their relics are exhumed ; while AEDTTOTO 

 (1759) made the important advance of classifying the rocks 

 into primary, secondary, and tertiary deposits. 



BALDASAEI (1767), in a memoir on a fossil jaw-bone (that 

 of a mastodon), enters into many philosophical speculations, 

 and establishes several important principles of geology. One 

 is, that the sea has certainly had a permanent abode on our 

 continents, a doctrine which he founds on the three con- 

 vincing facts, the regular distribution of marine objects in 

 the strata of mountains, the natural position presented by 

 corals and other zoophytes, and the circumstance that the 

 calcareous strata are perforated by PJiolades. He inculcated, 

 almost in the same words, the excellent principle adopted by 

 the early members of the Geological Society, to collect 

 materials before forming systems ; and states that it is with 

 this view that he calls attention to the fossil jaw in question, 

 which was procured from Monte Pullonico, in the territory 

 of Sienna, and which he correctly refers to those described 

 by Gruettard, as having been discovered in America and 

 India, and which are now recognised as those of the 

 mastodon. 



SOLDAKI (1789) is celebrated for the comprehensive 

 nature of his inquiries, and the philosophic accuracy of his 

 decisions. "While he devoted especial attention to micro- 

 scopic investigation, and published a splendid work on 



