144 Barrell — Growth of Knowledge of Earth Structure. 

 Rise and Decline of the Metamorphic Theory of Granite. 



Up to 1860 granite was regarded on the basis 

 of the facts of the field as essentially an intrusive 

 rock, but gneiss as a metamorphic product mostly of sedi- 

 mentary origin. It seemed as though sound methods of 

 research and interpretation were securely established. 

 Nevertheless, a new era of speculation and a modified 

 Wernerism arose at that time with a paper by T. Sterry 

 Hunt, marking a retrogression in the theory of granite 

 which lasted until his death in 1892. 



In November, 1859, Hunt read before the Geological 

 Society of London a paper on "Some Points in Chemical 

 Geology" in which he announced that igneous rocks are 

 in all cases simply fused and displaced sediments, the 

 fusion taking place by the rise of the earth's internal 

 heat into deeply buried and water-soaked masses of sedi- 

 ments (see 30, 133, 1860). The germ of this idea of 

 aqueo-igneous fusion was far older, due to Babbage and 

 John Herschel, neither of them geologists, but such 

 sweeping extensions of it had never before been pub- 

 lished. Hunt had the advantage of a wide acquaintance- 

 ship with geological literature and chemistry. He wrote 

 plausibly on chemical and theoretical geology, but his 

 views were not controlled by careful field observations. 

 In fact he wrote confidently on regions which apparently 

 he had never seen and where a limited amount of field 

 work would have shown him to have been fundamentally 

 in error. A man of egotistical temperament, he sought 

 to establish priority for himself in many subjects and in 

 order to cover the field made many poorly founded asser- 

 tions. Building on to another Wernerian idea, he held 

 that many metamorphic minerals had a chronologic value 

 comparable to fossils — staurolite for example indicating 

 a pre- Silurian age — and on this basis divided the crystal- 

 line rocks into five series. Although there is much of 

 value buried in Hunt's work it is difficult to disentangle 

 it, with the result that his writings were a disservice to 

 the science of geology. Although carrying much weight 

 in his lifetime, they have passed with his death nearly 

 into oblivion. 



Marcou, with a limited knowledge of American geol- 

 ogy, and but little respect for the opinions of others, had 

 published a geologic map of the United States containing 



