46 



ASSOCIATIONS FOR THE ADVANCEMENT OF SCIENCE. (BRITISH.) 



arranged in order, have been buried unde_r circum- 

 stances favorable to production of the various coaly 

 fuels, and then turned up in orderly disorder, ready 

 to the hand of man, and well adapted for his use in 

 this passage stage of his civilization and development, 

 helping him, when intelligent, active, careful, and 

 persevering, to higher ends. 



The following-named papers were read before 

 the section: "The Discovery of the Olenellus 

 Zone in the Northwest Highlands," and " Some 

 Recent Work of the Geological Survey on the 

 Archean Gneiss of the Northwest Highlands," 

 by Archibald Geikie ; " On the Cause of Monocli- 

 nal Flexure," by A. J. Jukes-Brown ; " On the 

 Continuity of the Kellaways Beds over Extended 

 Areas near Bedford," by A. C. G. Cameron ; " On 

 Colobodus, a Mesozoic Fish," by Montague 

 Brown ; " On the Discovery of the Southeastern 

 Coal Field," by Boyd Dawkins ; " The Cause of 

 an Ice Age," by Robert Ball ; " Recent Discover- 

 ies on the Relation of the Glacial Period in North 

 America to the Antiquity of Man," and " On Re- 

 cent Discoveries (human images) in the Pleisto- 

 cene Lava Beds of California and Idaho," by 

 George F. Wright, of Oberlin College ; " On Gla- 

 cial Action in Pembrokeshire," by H. Hicks ; and 

 " The Occurrence of Pachytheca Sphaerica and 

 Nematophycus in the Wenlock Beds at Tymawr 

 Quarry, Rumney," by John Storrie. 



D. Biology. Francis Darwin, of Christ's Col- 

 lege, Cambridge, presided over this section. His 

 address was as follows : 



A seedling plant in a state of nature grows straight 

 up, while its main root goes straight down. When it 

 is artificially 'displaced, both root and stem execute 

 certain curvatures by which they reach the vertical 

 once more. Such curvatures, whether executed in 

 relation to light, gravitation, or other influences, may 

 be grouped together as growth curvatures. I shall 

 principally deal with geotropic curvatures, or those 

 executed in relation to gravitation, but the phe_nom- 

 eqa in question form a natural group, and it will be 

 necessary to refer to heliotropism, and, indeed^ to 

 other growth curvatures. The history of the subject 

 divides into two branches, which will be considered 

 separately. When a displaced apogeotropic organ 

 curves so as to become once more vertical, two ques- 

 tions arise, which may be expressed thus : 1. How 

 does the plant recognize the vertical line ? how does 

 it know where the center of the earth is? 2. In what 

 way are the curvatures which bring it into the verti- 

 cal line executed ? The first is a question of irrita- 

 bility ; the second, of the mechanism of movement. 

 Sachs has pointed out that these two questions have 

 been confused. They should be kept as distinct as 

 the questions, How, by what nervous apparatus, does 

 an animal perceive changes in the external world ? 

 and How. by what muscular machinery, does it move in 

 relation to such changes ? 



He dealt separately with " irritability " and 

 " mechanism," and then treated of "circumnu- 

 tation," expressing his continued belief in the 

 views put forward in the " Power of Movement 

 in Plants," that circumnutation is a widely 

 spread phenomenon, even though it may not be 

 so 'widely spread as he and his father had sup- 

 posed. In conclusion he said : 



The relation between rectipetality and circumnu- 

 tation may be exemplified by an illustration, A 

 skillful bicycle rider runs very straight : the devia- 

 tions from the desired course are small ; whereas 

 a beginner deviates much. But the deviations are 

 of the same nature ; both are symptoms of the regu- 

 lating power of the rider. We may carry the anal- 



ogy further : just as growth curvature is the continu- 

 ance or exaggeration of a nutation in a definite di- 

 rection, so when the rider curves in his course he 

 does so by willful exaggeration of a "wobble." It 

 may be said that circumnutation is here reduced to 

 the rank of an accidental deviation from a right line. 

 But this does not seem necessarily the case. A bicy- 

 cle can not be ridden at all, unless it can "wobble." 

 In the same way it is possible that some degree of 

 circumnutation is correlated with growth in the man- 

 ner suggested above, owing to the need of regular 

 pauses in growth. Eectipetality would thus oe a 

 power by (which irregularities, inherent in growth, 

 are reduced to order and made subservient to recti- 

 linear ^growth. Circumnutation would be the out- 

 ward and visible sign of the process. 



Among the papers presented before this section 

 the following may be mentioned : " Description 

 of an Apparatus for the Cultivation of Small 

 Organisms in Hanging Drops under the Micro- 

 scope," by Marshall Ward ; " Non-sexual Forma- 

 tion of Spores in the Desmidiae," by A. W. Ben- 

 nett ; " Investigations on the Natural History of 

 the Friendly Islands," by J. J. Lister; " Hybrid 

 Ferns" and "Crossed Varieties," by E. J. Lowe ; 

 "Floating Leaves," by L. C. Miall; and "The 

 Artificial Production of Rhythm in Plants," by 

 Francis Darwin and Dorothea F. M. Pertz. 



E. Geography. The president of this section 

 was E. G. Ravenstein, who spoke on the " Field 

 of Geography." He first described the develop- 

 ment of cartography, which he illustrated by 

 an interesting collection of maps, and afterward 

 passed to the influence of geographical features 

 upon the destinies of the human race, and the 

 changes effected by man's conquests over na- 

 ture. These larger considerations, he contend- 

 ed, came legitimately within the " field of geog- 

 raphy," as well as the mapping and description 

 of the earth's surface. He said : 



Perhaps one of the most instructive illustrations of 

 the complex human agencies which tend to modify 

 the relative importance of geographical conditions is 

 presented to us by the Mediterranean. The time when 

 this inland sea was the center of civilization and of 

 the world's commerce, while the shores of western 

 Europe were only occasionally visited by venturesome 

 navigators or conquering Roman hosts, does not lie so 

 very far behind us. England at that period turned 

 her face toward Continental Europe, of which it was 

 a mere dependency. The prosperity of the Mediter- 

 ranean countries survived far into the middle ages, 

 and Italy at one time enjoyed the enviable position 

 of being the great distributor of the products of the 

 East, which found their way across the Alps into Ger- 

 many, and through the gates of Gibraltar to the exte- 

 rior ocean. But a change was brought about, partly 

 through the closing of the old Oriental trade routes 

 consequent upon the conquests of the Turks, partly 

 through the discovery of a New World and of a mari- 

 time highway to India. When Columbus returned 

 from the West Indies in 1493, and Vasco da Gama 

 brought the first cargo of spices from India, in 1499, 

 the star of Italy began to fade. And while the spices 

 of the Indies and the gold of Guinea poured wealth 

 into the lap of Portugal, and Spain grew opulent on 

 the silver mines of Mexico and Peru, Venice was 

 vainly beseeching the Sultan to reopen the old trade 

 route through the Ked Sea. The dominion of the sea 

 had passed from Italy to Spain and Portugal, and 

 later to the Dutch and English. But mark how 

 the great geographical discoveries of that age affect- 

 ed the relative geographical position of England. 

 England no longer lay on the skirts of the hab- 

 itable world ; it nad become its very center. And 

 this natural advantage was enhanced by the colo- 



