1878.] 



President's Address. 



51 



ceeding strokes ; and they also occur when the direction of the sound is 

 at right angles to that of the wind. Numerous observations were also 

 made on the influence of the wind, the results obtained by previous 

 observers being thereby confirmed. From his own observations, as well 

 as from the antecedent ones of Mr. Alexander Beazeley and Professor 

 Osborne Reynolds, Professor Tyndall concludes that the explanation of 

 this phenomenon given by Professor Stokes is the true one. 



Turning now to biological branches of Science, I find that the dis- 

 coveries and researches of the past five years in this department also 

 are far in advance of those of any previous period of equal length. 

 The " Challenger" Expedition was, in point of the magnitude of the 

 undertaking and completeness of its equipment, the rival of that for 

 observing the Transit of Venus. Its general results, as far as hitherto 

 made known, have been dwelt upon in my previous addresses, and 

 the publication of them in detail is being rapidly pushed forward. 

 Some very important papers by Mr. Moseley on the Corals collected 

 on the voyage have indeed been published in our " Transactions " 

 with admirable illustrations by himself. 



To the Botanist and Geologist no subject has a greater interest than 

 that of the conditions under which the successive Floras, which in- 

 habited the polar area, existed and were successively dispersed over 

 lower latitudes previous to their extinction, some in toto and over the 

 whole globe, while others, though extinct in the regions where they once 

 flourished, exist now only in lower latitudes under identical or under 

 representative forms. It is only during the last few years that, thanks to 

 the labours of those engaged in systematic Botany in tracing accurately 

 the directions of migrations of existing genera and species, and in 

 determining the affinities of the extinct ones, and of Palaeontologists 

 in referring the latter to their respective geological horizons, that 

 any material advance has been made towards a knowledge of the 

 origin and distribution of earlier and later Floras. I cannot better 

 illustrate the condition of this inquiry than by calling your attention 

 to two publications on the subject, which have appeared within the 

 last few months. 



As a contribution to the principles of Geographical Botany, Count 

 Gaston de Saporta's essay, entitled " L'Ancienne Vegetation Polaire " 

 (which appeared in the " Comptes Hendus " of the French Inter- 

 national Geographical Congress) is a very suggestive one, and having 

 regard especially to its author's eminence as a geologist and palaeonto- 

 logist, is sure to command attentive study. Although it maybe argued 

 that neither is solar nor terrestrial physics, nor Geology, nor Palaeonto- 

 logy in a sufficiently advanced condition to warrant the acceptation 

 as fully established truths of all the conclusions therein advanced, still 

 the array of facts adduced in evidence of these conclusions is very im- 



E 2 



