As a stratigraphical geologist he rendered much assistance on the Geological Survey of France, but in the course of time he gave his special attention to the study of volcanic phenomena and earthquakes, to minerals and rocks; and he was the first to introduce modern petrographical methods into France.
No assemblage of stratified rocks has received such careful and detailed examination as the Carboniferous system; consequently our knowledge of the stratigraphical sequence in isolated local areas, where the coals have been exploited, is very full.
In subdividing the strata of the Carboniferous system and correlating the major divisions in different areas, just as in other great systems, use has to be made of the fossil contents of the rocks; stratigraphical units, based on lithology, are useless for this purpose.
Their true stratigraphical position has not yet been ascertained, and it may appear that more than one group of rocks is included in the series.
Descriptions of the fossils, with some notes on stratigraphical questions, will be found in several of the volumes of the Palaeontologia Indica, published by the Geological Survey of India, Calcutta.
This is due in some degree to the energy of the early British geologists, whose work profoundly influenced all subsequent thought in the science, as may be seen by the general acceptation of so many of the English stratigraphical terms; but the natural conditions were such as to call forth and to stimulate this energy in an unusual way.
When we attempt to decipher the physical history of the country from the complicated record afforded by the stratigraphical palimpsest, we are checked at the outset by the dearth of information from being able to picture the geographical condition in the older Palaeozoic periods.
He early recognized the value of palaeontology in stratigraphical work; and he made important researches in the Rhenish mountains, in the Harz and Alpine districts.
This clear stratigraphical evidence is, however, so rarely found that much uncertainty still remains as to the true age of several of the floras now to be described.
This combination of circumstances has given the Graptoloidea a paramount stratigraphical importance as palaeontological indices of the detailed sequence and correlation of the Lower Palaeozoic rocks in general.