< 'orrespondencei 1 99 
Une excursion geologique dans lesMontagnes Rocheuses, M. Marcel- 
lin Boule. Assoc. Francaise ^Advancement des Sciences, 1893. 
Varietes: L'homme paleolithique dansl'Amerique duNord, M. Boule. 
The Mount Morgan gold mine, Australia, P. W. Sykes, 1892. 
The work of the Geological Survey, A. Geikie. Trans. Federated 
Inst. Mining Engineers, Vol. 5, pp. 142-168, 1893. 
Report of the Director General of the Geographical Survey and Mus. 
of Practical Geology for 1892, A. Geikie. Extr. 40th Rep. Sci. and Art 
Dept., 1893. 
Reunion extraordinarie dans la Velay et la Lozere, Sept. 14-24, 1893. 
Compte-rendu des seances de la Soc. Geol. de France, No. 14, 1893. 
Discussion of certain dissimilar occurrences of gold-bearing quartz, 
T. A. Rickard. 
Catalogue of a stratigraphical collection of Canadian rocks prepared 
for the World's Columbian Exposition, W. F. Ferrier. Geol. Sur. Can- 
ada, 1893. 
Datos para la Geologia de Mexico, Jose G. Aguilera andEzequiel Or- 
donez, 1893. 
VI. Proceedings of Scientific Laboratories. 
Bulletin of the Department of Geology, University of California, Vol. 
1, No. 3, Dec, 1893, contains: The eruptive Rocks of Point Bonita, F. 
Leslie Ransome. Vol. I, No. 4, Dec, 1893, contains: The Post-Pliocene 
diastrophism of the coast of southern California, A. C. Lawson. 
CORRESPONDENCE. 
Some Conditions of Ripple-mark. In a recent number of the 
American Geologist,* an interesting occurrence is described of highly- 
inclined bedding in a glacial sand-plain. This is explained as false bed- 
ding, on the ground that the real bedding consists of very faintly visi- 
ble ripple-marked layers, nearly horizontal, that have been deposited 
through a considerable thickness in regular series, the ripples in suc- 
cessive beds conforming precisely to those below. This is accounted 
for by a uniform current in one direction, depositing at a uniform rate 
materials "varied in point of size and weight," which became assorted 
by the rippling action, the larger fragments coming to rest in the 
troughs and the sand being packed closely on the long elopes of the 
ripple ridges. In this way a false bedding was built up by successive 
ripple-troughs and successive ripple-crests, dipping about forty degrees 
in the direction from which the ripple-forming current flowed. The 
section exposed is described as one hundred yards long and rif teen to 
twenty feet high; the ripple-marks have "regular and unvarying form." 
and the larger pebbles have an average diameter of two to two and a 
half inches. 
♦"False bedding in stratified drift deposits." HyJ. E. 8PUBB. Vol. Sin, January, 
1894. 
