344 Memoir of the Rev. Thomas Brown. 



in the rain water had destroyed the shells. Mr Brown, 

 remembering that the so-called shells of diatoms, being 

 siliceous, would not be destroyed by this gas, resolved to 

 search for diatoms in the terrace deposits, and diatoms were 

 found, which Professor Dickie of Aberdeen — an acknowledged 

 authority — identified as fresh water species. This seemed to 

 favour the first theory just mentioned. It might, indeed, be 

 asked were the data sufficient to warrant the inference ? 

 Whatever answer may be given, we are indebted to Mr 

 Brown for the introduction of this new element into these 

 discussions. 



1876. — Perhaps Dr Brown is seen at his scientific best in 

 the paper " On the Old River Terraces of the Earn and 

 Teith, viewed in connection with certain Proofs of the 

 Antiquity of Man," read before the Royal Society in the beginning 

 of 1876, and printed in volume xxvi. of the Transactions. 

 Before noticing the leading characteristics of this paper, I 

 ■ may refer to the circumstances which led to it, and specially 

 to the introduction of the speculative element in dealing with 

 Physical Geology phenomena. In 1838 M. Boucher de 

 Perthes, Abbeville, France, published his now well known 

 book, Be la Creation, in which he expressed the belief that 

 he would find traces of primeval man in the fluviatile gravels 

 of the Somme. In 1846, in another work entitled Be V 

 Industrie Primitive, ou les Arts et leur Origine, he intimated 

 that his anticipations had been fulfilled, and in 1847 his 

 Antiquites Celtique et Antediluvienne appeared, giving great 

 prominence to his discoveries in these river gravels. For 

 years little or no interest was taken in his works ; but about 

 1860 the attention of geologists, biologists, and archaeologists 

 was fixed on them, and a great controversy arose, in which 

 the giants of the time — Murchison, Lyell, Falconer, Carpenter, 

 and others — were conspicuous. The crucial enquiry came to 

 be "how was this valley formed?" Lyell thought that 

 "river erosion" will account for most of the phenomena, but 

 added, "I should infer considerable oscillations in the level 

 of the land in that part of France." Murchison took up 

 the same position, but claimed for the phenomeha the action 

 of much stronger and intenser forces than Lyell associated 

 with them. In a word, the interest taken in the alleged 

 facts and their discussion was because of the violent 



