THERE are spots, insignificant in themselves, which have a world-wide celebrity among those interested in certain pursuits or investigations. Such is Gheel to the alienist, Shide to the seismologist, or Bayreuth to the musician, and such, too, is Spiti, a barren and sparsely inhabited valley in the centre of the Himalayas, which has long been known to geologists for its extensive series of richly fossiliferous rocks. A district like this could not long escape the notice of the Geological Survey of India, and one of the earliest volumes of its memoirs is that by Dr. F. Stoliczka and F. R. Mallet. Published in 1864, this remained the standard, and practically the only, description of the geology of Spiti until the publication, in 1891, of Mr. C. L. Griesbach's memoir, in which, while adopting his predecessors' mapping in the main, he introduced great modifications in the sequence. Neither of these descriptions, however, is entitled to rank as more than a reconnaissance, but now we have the results of what may fairly be described as a survey of this region, and, in an interesting and clearly expressed memoir, Mr. Hayden has gone far towards clearing up the points which were in dispute. In all cases where he has found himself at variance with his predecessors' conclusions he has produced good evidence, and it is in one way satisfactory that he is generally in agreement with the one who can no longer defend his views.