N 1807 a Survey detachment was deputed by the Surveyor General of Bengal to explore the source of the Ganges: this was the first expedition to the Himalaya undertaken for purely geographical purposes. A hundred years have now elapsed, during which geographical and geological information has been steadily accumulating and we have at length reached a stage where there is danger of losing our way in a maze of unclassified detail it is therefore desirable to review our present position, to cc-ordinate our varied observations and to see how far we have progressed and what directions appear favourable for future lines of advance.