Geology, II., 1894, 33.) Further on in the same article, he writes of the deformation of the baselevel.' Although the writer has repeatedly made a similar use of the term, it now seems doubtful if it should be used so freely; and some such word as peneplain might serve to replace this extension of the original meaning of baselevel. This is the more advisable, when it is considered how very seldom a region is reduced sensibly to baselevel; how generally a long eroded surface still retains some faint inequality of form which should be expressed in its name. GEOMORPHOLOGY OF THE SOUTHERN APPA LACHIANS. THE interpretation of the development of geographical features in accordance with the general theory of baselevelling has received two notable contributions during the past year. The first is by Hayes and Campbell on the Geomorphology of the Southern Appalachians (Nat. Geogr. Magazine, VI., 1894, 63). The authors recognize the widespread occurrence of more or less fully denuded peneplains at two levels, one of late Cretaceous, the other of late Tertiary date, thus extending the conclusions reached by others farther to the north. They then proceed to measure the amount of deformation that the peneplains have suffered by drawing contour lines upon them. It appears very clearly that the axes of elevation along which these old lowlands have been arched up, coincide closely with the Appalachian axis; thus adding two more dates to the many others at which this line has been the scene of deformation. The tilting The tilting of the surface of the deformed peneplains is regarded as of importance in determining the capture and diversion of certain streams by their rivals; this principle being further illustrated by Campbell in a separate article on Tertiary changes in the drainage of southwestern Virginia' (Amer. Journ. Science, XLVIII., 1894, 21). GRADED RIVERS. A RIVER that ceased the active deepening of its valley is by various writers described as having reached its baselevel. Thus A. Winslow writes: "The streams of the prairie country . . . have, in large part, reached base level, and are developing meander plains." (Missouri Geol. Survey, VI., 1894, Lead and Zink deposits, 310.) H. Gannett figures a bit of the Great Plains of Colorado as 'near base level,' although the contour lines indicate altitudes of over 4000 feet. (Monogr. XXII., U. S. Geol. Survey, 1893, pl. viii.) Now it is true that streams which have ceased the active deepening of their valleys serve as local baselevels for their tributaries—as Powell's original definition stated; but it seems unadvisable to speak of these streams as themselves having reached baselevel; still less is the country which slopes down to them necessarily near' baselevel.' If the term is used in so general a sense as this, then an important feature in the development of rivers will remain undistinguished by any special name, and the attention of readers will not be forcibly brought to it. It is well known that when a river has cut down its valley and reduced its velocity to such a value that its capacity to do work in transporting waste is just equal to the work that it has to do, any further change in the profile of the stream-channel can take place only as fast as a change in the amount of landwaste offered to the streams shall allow. If the amount of waste slowly decreases, as is commonly the case, the stream will slowly assume a flatter and flatter slope (except so far as the development of meanders may lengthen its course and thus retard the deepening of its valley). If an increase in the amount of waste takes place after equality of capacity and task is reached, as sometimes happens, then the stream must aggrade its valley for a time. If the climate of the region changes, a new slope may be called for. Of two regions, similar in all respects except that one is made of resistant rocks, and the other of weak rocks, the first will develop a stronger relief during its mature dissection than the second. The Great Plains of the West are often referred to as a region of considerable elevation, in which, however, the rivers are unable to cut deep valleys on account of the rapid disintegration of the tributary slopes, and the consequent necessity of maintaining steepsloping channels in order that the streams may do their work of bearing the plentiful waste of the land to the sea. All this series of considerations is confused if it is said that a river which has established an equality between its capacity and its task is 'at baselevel.' From whatever profile of slope it began to work on, it has developed a profile of equilibrium, as certain French writers would phrase it; or, following a suggestion by G. K. Gilbert (Chicago Journal of Geology, II., 1894, 77), it has graded its slope; it is a graded river; it is almost balanced between degrading and aggrading its valley, and most of its activity may be given to lateral sapping. No better English term than 'grade' has been suggested for the expression of this important idea. GEOMORPHOGENY OF NORTHERN CALIFORNIA. THE second contribution to the general subject alluded to above is by A. C. Lawson, in account of the Geomorphogeny of the coast of northern California (Bull. Dept. Geol., Univ. of Cala., I., 1894, 241-242), which students of this new-named subject will do well to consult. Although only the report of a rapid reconnoissance, the paper announces the determination of a wellmarked, uplifted and dissected peneplain, in which a fully developed system of subsequent drainage is exhibited on an extensive scale. The district is recommended to students as an inviting field for further in vestigation. point that a constructional mass of resistant rocks will never at any stage of its denudation yield a topography that may be reached at certain stages in the denudation of a mass of weaker rocks; and he therefore suggests that in the accounts of topographic development, or geomorphogeny, a factor should be introduced indicative of the rate as well as of the stage of degradation of the region concerned. The author brings out the THE ESSENTIAL PRINCIPLES OF BASE LEVELLING. THE results gained in the two papers mentioned above, and in many other similar articles, are based on the essential principles of baselevelling: Any region must in time be reduced to a nearly featureless peneplain close to sea level; during the progress of its denudation, the forms assumed follow a tolerably well defined sequence, depending chiefly on the structure of the wasting mass; the features and arrangement of the drainage lines are essentially systematic and not arbitrary in their development. A generally accepted corollary of these principles is that a surface of denudation, having faint relief and no control by structure, can be produced only close to its controlling baselevel; and that such a surface represents the peneplain stage, attained close to the end of the cycle of denudation in which it was developed. It is evident that if a plain of denudation can be produced at a considerable altitude above baselevel, and independent of structure, then the conclusions of various investigators regarding land movements, based on the occurrence of elevated, warped or faulted peneplains, must be critically revised. It therefore behooves those who accept and employ the doctrine of baselevelling to examine carefully any alternative hypothesis by which peneplains are explained independently of baselevels. THE GEOGRAPHICAL EDUCATION OF OUR TOPOGRAPHERS. SOME engineers hold the opinion that it is not necessary for a topographer to have an understanding of the forms that he maps; it is sufficient for him simply to record what he sees without knowing its meaning. If all topographers could sketch with minute accuracy, if they all worked on a large scale and without limitation of time, they might perhaps manage to get along without an appreciative knowledge of the subject of their sketching. But the topographers by whom our maps are made cannot as a rule sketch with minute accuracy; and even if they could, their talent would be of little avail, for time could not be given to its use; moreover, maps of a scale large enough for minute accuracy are too expensive to undertake in so vast a country as ours. In many parts of the country the land is hardly worth as much per mile as it would cost to map it in an elaborate manner. Our maps must be made on a relatively moderate scale-seldom more than an inch to a mile; expensive detail cannot be permitted; and very slow work must give way to methods that will give results more rapidly. A great deal of our topographical work must be done by rapid sketching between measured points; the sketching must always be generalized; and every thing that will promote the production of good results from rapid and generalized sketching must be taught to the topographer. Looking at the subject in this practical manner, there can be no question that an appreciative understanding of topographical features is of great value. Rapid work by a topographer who does not understand the country before him will produce an unappreciative portrait. Generalizations by a surveyor who does not understand the relations of the forms that he generalizes will produce an unsuggestive and inaccurate map. A good understanding of physio graphy should therefore be regarded as an essential qualification of a topographer; and schools of engineering should see to it that adequate teaching of this subject is provided for their students. WINSLOW'S EXPLANATION OF THE MISSOURI PLAINS. SUCH an alternative hypothesis is offered by A. Winslow in his recent report on the lead and zinc deposits of Missouri (Geol. Survey of Missouri, Vol. VI., 1894). He describes certain parts of southern Missouri as exhibiting broad expanses of nearly flat land. A'prominent feature' of the district is the steepness of the hills adjacent to the stream valleys' (p. 306). Another part of the same region is a dissected plateau of carboniferous strata, terminating eastward in an irregular escarpment. The even interstream uplands of both plain and plateau are not regarded as of constructional origin, for the region has long been above sealevel; the possibility of either upland having once been a smooth peneplain of baselevel erosion is considered and rejected; and the following hypothesis is offered in its stead: "These prairie and plateau plains are primarily due to the fact that the slope of the surfaces has always been and continues slight. . . . . Consequently, the flow of the streams has been so sluggish that general atmospheric degradation has nearly kept pace with the corrasion of the streams and formation of the valleys. As a result, the whole surface has been denuded simultaneously. This condition is attributable, first, of course, to the gentleness of the original constructional slope; the horizontality of the stratification has helped to perpetuate it. . . . . . Secondarily as a factor in the production of these surfaces, it is probable that, where streams have corraded so slowly, broad flood plains have been developed at different levels at different times. Thus many flat stretches, which may be removed from the formative streams, are, perhaps, to be considered as of the nature of terraces marking the flood plains of a past stage of erosion" (p. 322, 323). Change of altitude of the region, or in other words, change of baselevel, is not referred to as essentially involved in the problem. The plateau surface, sloping to the west and terminating eastward in an escarpment Carboniferous strata, seems to depend on the greater resistance of these strata. It might be called a structural plain; a stripped surface on which general denudation has hesitated by reason of the endurance of the exposed strata, although the streams have deeply trenched it. With the prairie plains the case is different, for much of their area "is underlain by coal measure rocks, which are readily acted on by sub-aerial agents of erosion" (p. 323). If the streams of the region were not enclosed by steep-sided valleys, but wandered across the plains in channels hardly beneath the general surface level, then it might be admitted that the whole surface would waste away about as fast as the streams degraded their courses. But as the streams are in well-enclosed valleys, it does not seem logical to admit that the interstream plains can have wasted as fast as the valley forces. If the streams of the region even now distinctly incise its surface, all the more strongly must they have done so before long continued denudation had reduced its original altitude to its present altitude. The steep valley sides should long ago have been ravined, and the interstream plains should thus have been unevenly dissected. If this process had been long in progress, the region might already have reached or passed through the stage of most varied relief-topographical maturity; but it could not have attained an even surface distinctly above the level of its streams. Similarly, it does not seem admissible to suppose that streams, which are now run ning in rather narrow, steep-walled valleys, should ever, when still higher above baselevel, have had broad flood-plained valleys, beneath which they have incised the narrow existing valleys, yet without being prompted to this change of behavior by any change of altitude in the region. A decision as to the origin of these plains must be left to workers on the ground; but opinion as to the sufficiency of the process suggested for their production may be formed by any one who has familiarized himself with the general principles of denudation here involved. In the writer's mind Winslow's hypothesis does not invalidate the generally current principles of the baseleveling theory. GANNETT'S MANUAL OF TOPOGRAPHIC METHODS. THE general principle that the topographer should be well trained in physiography is strongly affirmed in Gannett's Manual of Topographic Methods (Monogr. XXII., U. S. Geol. Survey, 1893, issued in 1894). The volume contains a concise account of the surveys thus far undertaken in the United States; an account of the map now in progress by the U. S. Geological Survey, this containing much of interest to the geographical reader; and a treatment of the more technical matters of astronomical determination of position, horizontal location, secondary triangulation, sketching, and office work. In the chapter on sketching, there is an interesting discussion of the origin of topographic forms, with illustrations taken from various map sheets in the Survey office; this discussion being introduced 'as an aid in the interpretation of the various topographic forms which present themselves' to the topographer. Here we read the sound statement that "it is in the matter of generalization that the judgment of the topographer is most severely tested. He must be able to take a broad as well as a detailed view of the country; he must understand the meaning of its broad features, and then must be able to interpret details in the light of those features. Thus, and thus only, will he be competent to make just generalizations" (p. 107). THE UPLIFT OF THE EXISTING APPA- THE origin of topographic forms has as yet received so small a share of attention from the greater number of field geologists and geographers, and the presentation of the problems involved has as yet gained so little attention from teachers in schools of higher grade that contributions to the subject from a man of Mr. Gannett's experience and qualifications are of great value. Yet in certain parts it seems to the writer that his plan of presentation is open to criticism. He states first that topographic features originate by uplift, by deposition and by erosion. Under the heading of uplift, he writes: "The ridges and valleys of the Appalachian region are the result of uplifts, with numerous sharp folds and faults, which raised at various angles an alternation of hard and soft beds, from which erosion has since carved the existing alternations of ridge and valley" (p. 109). In spite of the In spite of the qualifications of a preceding paragraph, to the effect that forms produced by uplift are during and since their rise greatly carved by erosion, the reader can hardly acquire a correct understanding of the facts concerning the Appalachian ridges and valleys from Gannett's statement; nor can he easily acquire from the Appalachians an idea of the nature of forms produced by uplift with folding and faulting. Such forms can be illustrated best by the selection of young topographic districts, on which erosion has as yet made little advance. Our western country possesses many and excellent examples of this class. Furthermore, it is no more allowable to describe the Appalachian ridges and valleys as the 'result of uplifts, with numerous sharp folds and fault' than it would be to associate the fiords of Labrador with the ancient deformation of the old rocks of that region. The Appalachian uplifts with folds and faults have long ago been consumed; the uplift from which the existing ridges and valleys are carved was a broad arching of the region, without folding or faulting of perceptible measure. It is true that the up-arched mass possessed a structure given ages before by folding and faulting; but that more disorderly kind of uplift had little in common with the broad and even uplift of the region by which its present relief was initiated. The essay by Hayes and Campbell, already referred to, gives sufficient demonstration of this important conclusion. A FRENCH OPINION. THE following abstract from an essay entitled 'L'age des formes topographiques' by A. de Lapparent, the eminent geologist (Revue des questions scientifiques, Oct., 1894), expresses an opinion concerning the personnel of a topographic corps that is somewhat surprising as coming from France, where we had supposed that the propriety of the military control of official geographical work was unquestioned. De Lapparent writes in effect: The distraction of our professional geographers by the study of arbitrary political boundaries in the early part of this century would have been lessened if the work of detailed mapping had been left to men ready to interest themselves in the many questions provoked by the manifold forms of land relief. Unfortunately the reverse was done in decreeing that cartography should be exclusively a function of the department of war. Up to 1830 there was in France an excellent institution, of the geographical engineers. Well prepared in the École polytechnique, the that |