Clouds

MORE attention has probably been given to the study of clouds at Blue Hill Observatory, Massachusetts, than anywhere else in the world, and the appearance of a volume containing the cream of the many fine photographs of clouds taken there, in addition to a selection of photographs from other sources, is to be welcomed. The reproduction of these varies. According to the very high standard of the present day, many of the photographs of cirrus cloud can only be classed as poor, the essential fibrous structure being replaced by a wool-like appearance almost suggestive of fracto-cumulus at a first glance. Even the comparatively easily reproducible cumulus and cumulo-nimbus are not as a rule entirely satisfactory, a common fault being the total lack of detail in those parts of the cloud that are in shadow. Against these drawbacks must be set the exceptionally interesting view-point from which some of the low forms of cloud have been photographed, and the amount of light thrown upon their physical structure in consequence. It will come as a revelation to those who have not had many opportunities of studying clouds from above, the extent to which fog sheets can form ‘surges’ and cascades when drifting over hills, without being broken up or dissolved.Clouds.Prof. Alexander McAdie. Pp. iii + 22 + 52 plates. (Readville, Mass.: Blue Hill Observatory.)