484 



NATURE 



[September 16, 1897 



other plants to injure ; but it is another matter to kill the same 

 weeds growing in a lawn or a flower-bed, where we have to pay 

 attention to the neighbouring plants. 



Experiments in the open, simple in themselves, but conducted 

 intelligently and with due regard to the rigorous demands of 

 science, can alone determine these questions. 



Brewers have long known that burning sulphur in the barrels 

 will rid these barrels of the rnoulds and yeasts growing on their 

 damp beer-soaked sides ; and Berkeley saw clearly that sulphur 

 could be applied to the outside of plants on which such fungi as 

 the hop- or grape-mildew, &c., are growing, the critical period 

 being when the spores are germinating, so that the slowly oxi- 

 dising sulphur should evolve sulphurous acid in just sufficient 

 quantities to destroy the delicate germs without injuring the 

 leaves. And even better results have been attained with 

 Bordeaux mixture. 



But it is clear that this can only be done with an intelligent 

 appreciation of the life-history of the fungus, and a knowledge 

 of when the germinating stage is at hand. The successes ob- 

 tained in France and America with Bordeaux mixture attest 

 this. 



It would obviously be absurd to powder sulphur or spray 

 liquids over plants attacked by bunt- or smut-fungi, for we know 

 that the germ-tubes only infect the germinating grain as its first 

 root emerges. Here, as was shown long ago, and especially by 

 the experiments of Hoffmann, Klihn, and l5e Bary, the practice 

 known as " dressing the grain" must be followed. Knowing 

 that the spores of the fungus are attached to the grain, or to 

 particles of soil around, the efforts must be dfrected to covering 

 the outside of the grain with an antiseptic which is strong enough 

 to kill the germs but not the grain. If the land is known to be 

 clean, the grain may be immersed in hot water, the temperature 

 being experimentally determined, and high enough to kill the 

 •spores but not the wheat, and so on. In these matters also the 

 American stations have done good work. 



Neither of these classes of treatment can be adopted, on the 

 other hand, for diseases such as " Finger and Toes," where we 

 have a delicate slime-fungus making its way into the roots already 

 in the soil ; but, here again, intelligently devised experiments, 

 such as those of Somerville and Massee, have shown that liming 

 the soil renders it so unfavourable to this disease that it can be 

 coped with. 



And similarly with other diseases ; the particular methods of 

 dealing with the "damping-off " of seedlings, "dry-rot" in 

 timber, the various diseases of trees, and so on, do and must 

 differ in each case, and the guiding principle must be always 

 the same — having learnt all that can be learnt of the habits of 

 the fungus and of the host, and of the relationships of each to 

 the other and the environment, to see how it is possible to step 

 in at the critical moment and interfere with these relationships 

 in the direction desired by human interests. 



The whole matter thus resolves itself into a study of variation 

 — a purely experimental inquiry into complex biological relation- 

 ships, and it is encouraging to see that this is being understood 

 in the large American and other stations, which are distinguish- 

 ing themselves by their efforts. 



GEOLOGY AT THE BRITISH ASSOCIATION. 

 'T'HE attendance of British geologists at this meeting of the 

 -'■ Association was not large, owing, no doubt, to the counter- 

 attractions of the International Geological Congress in Russia, 

 which drew away also some American geologists who might 

 otherwise have attended. But in spite of this, the section was, 

 on the whole, well attended, and its work was exceptionally 

 arduous and interesting. Though with the exception of the 

 reports of Committees, there were only three papers exclusively 

 British in their scope, the large number of contributions on 

 North American subjects more than made up the deficiency, 

 and gave to this meeting a distinctive character. It is signifi- 

 cant of the vitality of earth study on the American side of the 

 Atlantic that the papers should have been, upon the whole, 

 well above the average of other meetings. 



Contributions of merely local interest were almost absent, and 

 again and again one was struck by the breadth of view and 

 vigour of generalisation which marked the work submitted to 

 the section. The presence of numerous distinguished Canadian 

 and American geologists, many of the latter coming from the 

 Detroit meeting of the sister Association, furnished an audience 



ready to grasp and to criticise the views brought forward, and in 

 some instances discussions commenced in Detroit were con- 

 tinued in Toronto. It was, indeed, only the amount of work 

 to be got through which limited the debates. The Glacial 

 papers were exceptionally numerous and full of instruction for 

 the European geologist, while that of Prof. Penck must have 

 had a high interest for American glacialists. It was possible, 

 on the day set apart for these papers, to arrange a series which 

 should span the continent from the Atlantic to the Pacific, and thus 

 to bring before the listener a comprehensive view of the whole 

 bearings of the subject in North America. It is noteworthy 

 that neither in the papers nor in the discussion was there a 

 single dissentient from the view that ice-sheets covering the 

 northern portions of the continent had formed the drifts. This 

 seems to be taken as established beyond all doubt in North 

 America. 



Next after the Glacial papers in numbers and importance were 

 those dealing with the Archaean and Palaeozoic rocks, these 

 again reflecting the locale of the meeting. 



Petrological studies were also fully represented, Init Palaeon- 

 tology was comparatively neglected, though a feature of the 

 meeting was the special exhibition of several collections of North 

 American fossils. Those to excite the greatest attention were 

 the beautifully preserved trilobites showing the antennae and 

 pedal appendages, collected from the Utica Shales of Rome, 

 N.Y., by Dr. C. E. Beecher, and exhibited by Dr. Ami. 



The excursions arranged for the geologists were highly 

 successful and most enjoyable. Niagara was visited under the 

 leadership of Mr. G. K. Gilbert, of the U.S. Geological Survey; 

 the inter-glacial deposits of the Don Valley and Scarborough 

 Heights, under the guidance of Prof A. P. Coleman ; while 

 Dr. J. W. Spencer pointed out the main features of the Iroquois 

 Beach, a deformed post-glacial shore-line. Of the long excursion 

 to the Pacific Coast, to which the Canadian Pacific Railway Co. 

 has munificently invited a large party of members, it is at the 

 time of writing too early to speak, but this is being anticipated 

 by all invited as the fitting close of a most enjoyable and 

 memorable meeting. The geologists on this excursion will he 

 under the guidance of their President, Dr. G. M. Dawson, and 

 their Secretary, Prof. A. P. Coleman. 



The sectional work of the meeting commenced on Thursday, 

 August 19, with the President's address, an able exposition of 

 the present state of our knowledge respecting the most ancient 

 rocks of Canada, of which, as it has already been given in full 

 in our columns, it is necessary now only to record the favourable 

 reception by the meeting. 



Next followed a group of papers treating of the pre- Palaeozoic 

 and Palaeozoic rocks of North America. Dr. L. W. Bailey 

 described some typical sections in south-western Nova Scotia, 

 in which he showed the succession of the Cambrian rocks of 

 that region and their relation to the granite axis. Dr. R. W. 

 Ells discussed problems in Quebec geology, dealing with the 

 origin of the fundamental gneiss and the Grenville series, and 

 their relations to the Hastings series and the oldest fossiliferous 

 rocks. Mr. J. C. Branner traced the former extension of the 

 Appalachians across Mississippi, Louisana, and Texas beneath 

 the newer rocks. 



A most interesting paper at this session was that of Dr. F. D. 

 Adams and Mr. J. 1'. Nicholson, entitled "Preliminary notice of 

 some experiments on the flow of rocks," in which the authors re- 

 lated how they had placed, accurately-fitting columns of Carrara 

 marble about 4 cm. long by 2 cm. diameter within specially 

 prepared tubes of Swedish iron, and had subjected them to extreme 

 pressure gradually applied. The rock yielded like a plastic 

 substance, and bulged the enclosing tube. In one experiment 

 the column was reduced from 40 mm. to 21 mm. in height, the 

 deformed marble remaining quite firm and compact, though not 

 so hard as the original rock. When sliced and examined 

 microscopically, polysynthetic twinning of the calcite crystals 

 and other indications of strain were observable. These very 

 suggestive experiments are to be continued, and it is certain 

 that all students of dynamic geology will follow the results with 

 keen attention. At a later session Dr. Adams dealt with the 

 structure and origin of certain rocks of the Laurentian system, 

 his conclusions corresponding with those of European workers 

 on rocks of similar type, since he showed by chemical analysis 

 and microscopic examination that the foliated rocks included 

 two distinct and separable types — the one almost certainly 

 highly altered sediments, and the other of igneous origin. 



At Friday's session most of the Glacial papers were read. 



NO. 1455. VOL. 56] 



