376 



NA TURE 



[February 15, 1906 



RECENT REPORTS OF GEOLOGICAL 



SURVEYS.' 



Cleavage. 



""THE subject of rock cleavage is one of perennial interest ; 



only a short time ago were Dr. Becker's views noticed 

 in these columns, views founded upon experiment and 

 analysis. Now, Dr. Leith (i) lays before us his reading of 

 the same problems after attacking them by the way of 

 micro-sections and field observations, the author makes 

 the term "rock cleavage" very comprehensive; he re- 

 cognises among cleavable rocks two broad divisions, which 

 he calls respectively protoclase, or original cleavage rock, 

 and metaclase, or secondary cleavage rock. The former 

 class includes such structures as bedding in sediments and 

 flow structure in lavas; the latter class is considered under 

 the heads "fracture cleavage" and "flow cleavage." 

 Fracture cleavage is conditioned by the existence of in- 

 cipient or cemented and welded parallel fractures, and is 

 independent of the parallel arrangement of the mineral 

 constituents. Flow cleavage is conditioned solely by a 

 parallel arrangement of the minerals. The one is a pheno- 

 menon of the zone of fracture, the other of the zone of 

 Howage in the lithosphere. Fracture cleavage is made 

 to include, wholly or in part, those structures that have 

 been variously described as close-joint-cleavage, false 



Chloritoid cry 



cleavage, strain-slip-cleavage, slip cleavage, ausweichungs 

 cleavage, rift and fissility in part (the term is retained for 

 closely spaced parallel partings). Flow cleavage includes, 

 wholly or in part, the ultimate cleavage of Sorby, 

 " cleavage " of most authors, slaty i leavage, schistosity, 

 and parallel structures in certain gneisses. Flow cleavage 

 is a molecular phenomenon, and the dominating factor in 

 its production is re-crystallisation. Much space is devoted 

 to the study of the behaviour of the more important rock- 

 forming minerals in relation to the direction of the cleavage 

 in rocks, and many thin slices have been examined to 

 determine how far there existed a parallelism between the 



ByC. 



Indu< 



1 (0 Bulletin 23 



(2) Bulletin 243". 

 Eckel. 



(3) Bulletin 2S2, 1905, " Preliminary Repor 

 Resources of Central Oregon.'' By I C Rui 



(4) Bulletin 235. 1904, " A Geological Recor 

 Range." By G. O. Smith and F. C. Calkins. 



(s) Bulletin 242, rQo 4 , "Geology of the Hud 

 Hoosic and the Kinderhook." By T. N. Dale. 



(6) Bulletin 254, 1904. " Report of Progress in the Geological Re 

 of the Cripple Creek District, Colorado." By Waldemar lander 

 F. I.. R 



(7) 



Ey E. C. 



the Geology and Water 



across the Cascade 



Valley between the 



;e-survey 



1905, " Petrography and Geology of the Igneous Rocks 

 of the Highwood Mountains Montana." By L. V. Pirsson. 



(8) Twenly-lrflh Annual Report of the U.S. Geological Survey, 1903-4. 



(9) Indiana, Department of Geoloey and Natural Resources, Twenty- 

 ninth Annual Report, 1904. By W. S. Blatchley. 



(ro) Canada: Summary Report of the Geological Survey Department cf 

 Canada for the Calendar year 1904 (1905). 



NO. 1854, VOL. J?,] 



cleavage of the rock and dimensional and vector properties 

 of given mineral species. 



The bulletin is evidently the result of a great deal of 

 work, and contains a clear statement of the author's views ; 

 the illustrations are excellent, and it must be read by all 

 interested in the subject, but it cannot be said greatly to 

 advance our knowledge. 



The Geology of Cements. 



Several reports have appeared from time to time dealing 

 with the raw cement materials of individual States ; in 

 Bulletin No. 243, E. C. Eckel (2) summarises the available 

 information for the United States as a whole. " The 

 object has been to treat the subject from the geological 

 rather than from the technical standpoint, although the 

 technology of the cement manufacture is also discussed 

 with sufficient fulness for the purpose of the report." 

 While mainly a compilation, and bearing the impress of 

 composite authorship, there is in this volume an air of 

 freshness about the facts and of uniformity about their 

 presentation which is doubtless due to the circumstance 

 that Mr. Eckel personally visited every district in which 

 cement is being produced, and examined nearly every plant 

 in operation. Nor were the undeveloped deposits of cement 

 material neglected. 



The bulk of the report is devoted to Portland cement 

 materials in the several States; the geological characters 

 and relationships of the limestones, clays, and natural 

 cement rock are clearly explained, abundant analyses are 

 shown, and the peculiar local conditions of transport and 

 fuel, as well as the available markets, are briefly discussed. 

 The cement materials are derived from rocks of the most 

 diverse geological age, ranging from Cambrian up to recent 

 marls and alluvial silt-. Short sections are given to the 

 " natural " cement resourci s and to the Puzzolan cements. 

 We noticed in the section on the grinding of raw materials 

 no reference to the influence of the degree of fineness upon 

 the temperature required for a suitable clinker. 



General Geology. 



The average British geologist, if his range of vision is 

 not quite limited bv the importance of the exposure in his 

 own back garden, if he can momentarily turn from pebble- 

 picking and the unravelling of zones, may enjoy by 

 following Prof. Russell across central Oregon, a pleasant 

 and profitable, if somewhat tantalising, hour. The region 

 included in this preliminary report (3) comprises the country 

 between the Snake River on the east and the Cascade 

 Range on the west, and thus takes in the extreme northern 

 part of the Great Basin. 



The predominant rocks of central Oregon are volcanic ; 

 an older series of rhyolites and andesites is succeeded by 

 a younger series of basaltic rocks, which are again 

 followed in the Pauline Lake district by andesitic outbursts. 

 The oldest of the rocks dates from early Tertiary times ; 

 Ihe youngest may be only a few centuries old. 



The sedimentary rocks are represented by soft clays, 

 sands and volcanic dust of Tertiary age. The most con- 

 spicuous elevations in central Oregon are of volcanic 

 origin ; many are old worn-down craters and peaks, but 

 young volcanoes, particularly as the Cascades are 

 approached, are exceedingly abundant. " Their cones, so 

 recent in numerous instances that erosion has not yet 

 broken their crater rims, are so numerous that 50 or 

 more may frequently be counted in a single view, while 

 a change of a few miles in the position of the observer 

 brings perhaps as many more within the range of vision." 



Many interesting features in the water supply and drain- 

 age of the country are described in these pages, but none 

 exceeds in interesl the fast inating story of the Deschutes 

 River, about the point where it is joined by its tributary 

 the Crooked River. First we find that the Deschutes in 

 Tertiary times had eroded a great valley twenty to thirty 

 miles wide in parts ; then most of this valley was filled to 

 a depth of more than 700 feet by water-borne volcanic 

 dusl and lapilli with a little sand and clay; this was 

 followed by a sheet of basalt some 80 feet thick. Displaced 

 in this way from their old courses, the Deschutes and its 

 tributaries cut fresh channels and made canyons in the 

 new material 800 feet deep and about one mile wide, until 



