January 19, 1893] 



NATURE 



275 



fact, that when his communication on the discovery of 

 glacial markings was read before the Geological Society 

 of London, it was received with scepticism by Prof. 

 Bonney (and, let us add, though the author does not, by 

 Dr. Blandford also). On turning to the Journal of the 

 Society we find that Prof. Bonney considered the 

 observations then adduced by Von Lendenfeld as in- 

 sufficient to establish his conclusions, and in this opinion 

 we fancy most geologists will be inclined to agree with 

 liim. That the conclusions were right after all is a 

 different matter. It is to be regretted that even in this, 

 his latest published summary, Von Lendenfeld does not 

 always supply us with facts on which we can base an 

 independent judgment. The personal opinion of an 

 observer, however skilled, can be no sufficient substitute 

 for these. A single instance will suffice. An important 

 joint expedition was undertaken by the author and 

 Mr. Stirling to examine into the accuracy of the 

 latter's statements as to the downward extension of 

 the ice. After several pages of interesting traveller's 

 gossip we reach the result in words much to the following 

 effect :— "After three-quarters of an hour's ride in the valley 

 bottom we reached an old moraine, which we investigated 

 closely. A dam 35 metres high and 200 broad composed 

 of various {verschieden) great blocks of rocks with 

 sharp angles stretched across the valley. A brook flowed 

 through the middle. We are here at a height of from 900 

 to 1000 metres, and since it is a veritable moraine Stirling 

 is right and our dispute is ended." 



We will not offend the susceptibilities of the author by 

 questioning whether this is really a moraine : probably it 

 is ; but no convincing proof of the fact appears in the 

 description. One would like to know whether other signs 

 of ice-action were observed in the immediate neighbour- 

 hood, in what respects the fragments differed from each 

 other and from those of the adjacent valley slopes, and 

 especially what evidence existed to show that they had 

 been carried down the valley, and how far they are 

 removed from their source. This information could have 

 been conveyed in a few words, and would have been 

 welcomed by inquiring minds, who now may wonder 

 whether after all this dam could by any chance be merely 

 the remains of an ancient landslip. New Zealand 

 is introduced to us on p. 161, and after a short historical 

 account we pass on to the New Zealand Alps and 

 fjords. With regard to the latter the author stoutly 

 maintains their glacial origin : one of his chief 

 arguments resting on their great epth as compared 

 with the sea into which they open. They are apparently 

 submerged rock basins, but although the author may be 

 right in his contention that they are not merely moraine- 

 dammed valleys, yet he altogether overlooks another 

 more probable explanation, depending on unequal 

 subsidence : submergence of the land has certainly 

 taken place, and one has only to concede that the central 

 mountain masses have sunk to a greater extent than the 

 adjacent sea-floor to understand how the previously 

 existing valleys would be converted into fjords. The 

 greatest depth of Milford Sound is 360 metres, and one 

 must travel (so our author tells us) at least 100 kilometres 

 from the coast before this depth is reached at sea ; now 

 as the watershed is distant only 30 kilometres from the 

 coast, it is at least as probable, considering the gradient, 

 that we have to do here with differential movements of 

 the land, as with locally concentrated erosive action. 



An ingenious attempt to explain the last glacial episode 

 leads to several bold generalizations. The author 

 commences with the assertion that the whole of the 

 southern hemisphere is at present much more severely 

 glaciated than the northern, indeed he goes so far as to 

 state that the northern hemisphere in the middle of the 

 ice period was not much more severely glaciated than the 

 southern is now. Since the mean temperature of the 

 southern is not lower than that of the northern hemi- 



sphere the reason for its excessive glaciation must lie in a 

 more uniform climate and a damper atmosphere ; and 

 these again are a direct consequence of the greater 

 extent of the oceanic surface. 



Let us now suppose the sea-level in the northern hemi- 

 sphere to rise 100 metres, the lowlands will become 

 submerged (as during the last glacial episode they 

 apparently were) the climatal conditions will then 

 approach those now prevailing in the southern hemi- 

 sphere, and excessive glaciation will result. 



But in the southern hemisphere also, the ice was 

 formerly of much greater extent, and this is not susceptible 

 of the same explanation, since a depression of the land 

 would not greatly affect the existing climate. What, 

 however, would be the effect of a depression of the sea 

 level ? The submarine slopes of most of the land in the 

 southern hemisphere are so steep that the present 

 distribution of land and sea would not be largely 

 modified, though the latter should sink 300 metres ; on the 

 other hand, the increase in the height of mountains 

 (300 metres) would lead to a descent of the snow line, 

 the growth of snow fields, and a corresponding enlarge- 

 ment of glaciers. Thus the glacial episode in the 

 northern hemisphere might be attributed to an elevation 

 of the sea-level, that in the southern to its depression ; 

 and these changes of level may have been produced by a 

 bodily movement of the ocean waters from one hemi- 

 sphere to the other, a result itself possibly due to a 

 shifting of the centre of gravity of the earth. The 

 author does not explain how to shift the centre of gravity 

 of the earth. 



We notice that the author speaks with disrespect of the 

 maps of the Tasman glacier by Mr, W. S. Green, stating 

 that they are nothing like so good as Von Haast's ; since 

 however, later explorers prefer them to Von Lendenfeld's 

 own, it would appear that we have here a descending 

 scale of excellence. 



After pointing out the failure of Mr. Green to reach 

 the actual summit of Mount Cook, the author gives a 

 glowing account of a successful ascent of his own, not of 

 Mount Cook however, but of the Hochstetter Dome ! 

 He therefore claims to be the first who has set foot on the 

 top of a high mountain in New Zealand. We offer him 

 our congratulations. 



In commenting on the author's style, which in its 

 lucidity is far more English than German, we must offer 

 a serious protest against his manner of using what he 

 terms our " transcendentally intense adjective." Bob 

 Acres' remark that, " The best terms will grow obsolete. 

 Damns have had their day," does not appear to apply 

 to Australia, where, to judge from our author, they flourish 

 along with other survivors of a Mesozoic age. 



AMERICAN FORESTRY} 



COMPETENT English authorities on forestry are so 

 rare that no apology is needed for presenting some 

 extracts from a translation from the German, of an im- 

 portant paper by Sir D. Brandis on American forestry. 

 This is in continuation of a similar translation which 

 appeared about a year ago in the columns of Nature 

 (vol. xliv. p. 60). 



Upwards of I, ooo,ocx) acres of forest are required for 

 the annual supply of wooden sleepers for European rail- 

 ways. These forests are properly managed so as to yield 

 a steady return, whilst nothing of the kind can be said ot 

 American forests. This explains why German foresters 

 are interested in watching the progress of forest destruction 

 in America, where it is now merely a question of ten or 



■ " The Silvaof North America." By C. S. Sergent, vols, i.-iv. (Bcton 

 and New York. Houghton, MifBin and Co., 1801-92). Notes on the abov« by 

 SirD. Brandis. K.C.I.E., ¥.V>..?,.,\nZeitscftri/t fiir Forst und fagdwesen, 

 October, 1892. 



NO. 



12 12. VOL. 47] 



