August 15, 1878] 



NATURE 



415 



range of mathematical science, so indefinitely may it extend 

 beyond our actual powers of manipulation, that at some moments 

 we are inclined to fall down with even more than reverence 

 before her majestic presence. But so strictly limited are her 

 promises and powers, about so much that we might wish • to 

 know does she offer no information whatever, that at other 

 moments we are fain to call her results but a vain thing, and to 

 reject them as a stone when we had asked for bread. If one 

 aspect of the subject encourages our hopes, so does the other 

 tend to chasten our desires ; and he is perhaps the wisest, and in 

 the long run the happiest among his fellows, who has learnt not 

 only mathematics, but also the larger lesson which they indirectly 

 teach, namely, to temper our aspirations to that which is possible, 

 to moderate our desires to that which is attainable, to restrict 

 our hopes to that of which accomplishment, if not immediately 

 practicable, is at least distinctly within the range of conception. 

 That which is at present beyond our ken may, at some period 

 and in some manner as yet unknown to us, fall within our 

 grasp ; but our science teaches ns, while ever yearning with 

 Goethe for " Light, more light," to concentrate our attention 

 upon that of which our powers are capable, and contentedly 

 to leave for future experience the solution of problems to which 

 we can at present say neither yea nor nay. 



It is within the region thus indicated that knowledge in the 

 true sense of the word is to be sought. Other modes of 

 influence there are in society and in individual life, other forms 

 of energy beside that of intellect. There is the potential energy 

 of sjTnpathy, the actual energy of work ; there are the vicissi- 

 tudes of life, the diversity of circumstance, health, and disease, 

 and all the perplexing issues, whether for good or for evil, of 

 impulse and of passion. But although the book of life cannot 

 at present be read by the light of science alone, nor the wayfarers 

 be satisfied by the few loaves of knowledge now in our hands, 

 yet it would be difficult to overstate the almost miraculous 

 increase which may be produced by a liberal distribution of what 

 we already have, and by a restriction of our cravings within the 

 limits of possibility. 



In proportion as method is better than impulse, deliberate 

 purpose than erratic action, the clear glow of sunshine than 

 irregular reflection, and definite utterances than an uncertain 

 sound ; in proportion as knowledge is better than surmise, proof 

 than opinion ; in that proportion will the mathematician value a 

 discrimination between the certain and the uncertain, and a just 

 estimate of the issues which depend upon one motive power or 

 the other. While on the one hand he accords to his neighbours 

 full liberty to regard the unknown in whatever way they are led 

 by the noblest powers that they possess, so on the other he 

 claims an equal right to draw a clear line of demarcation 

 between that which is a matter of knowledge, and that which is 

 at all events something else, and to treat the one category as 

 fairly claiming our assent, the other as open to further evidence. 

 And yet, when he sees around him those whose aspirations are 

 so fair, whose impulses so strong, whose receptive faculties so 

 sensitive, as to give objective reality to what is often but a reflex 

 from themselves, or a projected image of their own experience, 

 he will be willing to admit that there are influences which he 

 cannot as yet either fathom or measure, but whose operation he 

 must recognise among the facts of our existence. 



SECTION C. 



GEOLOGY. 



Opening Address by the President, John Evans, D.C.L., 

 F.R.S., F.G.S., &c. 



In opening the proceedings of this Section, I cannot but call 

 attention to the fact that the present is the third occasion on 

 which the British Association has met in this city, its first meet- 

 ing here having taken place in the year 1835, or forty-three 

 years ago. On that occasion, as indeed for many years after- 

 wards, the two distinct, though to some extent cognate branches 

 of study, geology and geography, were classed in the same 

 section, and its president was a man of whom Irish science may 

 well be proud, and who, I am thankful to say, is still living to 

 enjoy his well-deserved honours — the veteran geologist. Sir 

 Richard John Griffith, the author of the first geological map of 

 Ireland. It seems hardly credible that the construction of this 

 map was commenced in the summer of 1812, or sixty-six years 

 ago ; but the records of the Geological Society of London testify 

 to the still more remarkable fact that Sir Richard Griffith was 

 elected a fellow of that Society in 1808 — seventy years ago. 



Indeed, in 1854, when the Wollaston medal was awarded to the 

 then Dr. Griffith, the president, the late Prof. Edward Forbes, 

 spoke as he said reverentially to one of the earliest members of 

 the Society, and to a geologist who appeared in print before he, 

 the president, was bom. It was well said on that occasion that 

 the map lately mentioned was one of the most remarkable geo- 

 logical maps ever produced by a single geologist ; and I make 

 no doubt that those who are at present engaged on the Geological 

 Survey of this island will testify, as did their predecessors, to 

 the value of this "surprising monument of observation and 

 skill." When speaking of the Geological Survey of Ireland, it 

 will not, I am sure, be thought out of place if I offer here a 

 tribute of respect to the memory of one who was originally a 

 student in the college within whose walls we are assembled, and 

 who subsequently occupied posts of the highest importance in 

 connection with the Geological Society of Dublin and the Geo- 

 logical Survey of Ireland, besides filling the professorial Chair 

 of Geology in this University : I mean Dr. Thomas Oldham, 

 the late Director of the Geological Survey of India. With the 

 marvellous amount of work which he was enabled to accomplish 

 in that country you are all acquainted, and you will all share in 

 the regret that the period of his well-earned retirement — that 

 "requies optimorum meritorum " — should have been so quickly 

 cut short by death. His name will, however, long survive, and 

 future students of geology will have no difficulty in recognising 

 the distinguished labourer in their science after whom the Cam- 

 brian Oldhamia of the Wicklow hills so worthily received its name. 



But to return to this Association. 



On the next occasion of its meeting in Dublin, in 1857, Sec- 

 tion C had become devoted to geology alone, and geography 

 was excluded, the president being Lord Talbot de Malahide, a 

 nobleman whom also we still have among us, and who is alike 

 well kno^vn to archaeologists and geologists. 



As the last meeting of the Association in this city took place 

 twenty-one years ago, it would at first sight appear that in 

 opening our proceedings I might with propriety dwell on the 

 progress which has been made within that period in the develop- 

 ment of the geology of Ireland. I must, however, remind you 

 that it is only four years since the Association held its meeting in 

 what I may almost call the neighboming town of Belfast, when 

 the accomplished chief of the Geological Survey in Ireland 

 presided over this section and delivered an address, in which 

 some of the more interesting features of the country, especially 

 those of the volcanic district of the north-east of this island, were 

 discussed. During the present year, moreover, he has published 

 his comprehensive work on the "Physical Geology and Geo- 

 graphy of Ireland," which I commend to you as far more likely 

 to call yoiu: attention to the characteristic features of the country 

 and the latest discoveries with regard to its geology than any- 

 thing I could compile. 



In addition to this, there has appeared during the present year 

 another interesting volume, which records the impressions of a 

 highly intelligent foreign geologist on visiting this country. I 

 mean the " Aus Irland " of Dr. Arnold von Lassaulx, Professor 

 of Mineralogy in the University of Breslau. For this volume, 

 in which shrewd remarks on the country and its inhabitants are 

 mingled with geological observations and valuable comparisons 

 of the Irish formations with those of other countries, we are 

 indebted to the meeting of the British Association having been 

 held two years ago at Glasgow, which attracted the author to 

 visit the British Islands. 



So much having lately been published upon the geology of 

 this country, I shall content myself with making a very few- 

 general observations with regard to it, and propose subsequently 

 to touch briefly on some of those questions which, within the 

 last twelve months, have occupied the attention of those who 

 are engaged in the advancement of our science. 



As to the geology of this country, I may observe that we are 

 here assembled just on the edge of that great central plain which 

 forms so important a feature in the map of Ireland, and which- 

 stretches from Dublin Bay on the east coast, to Galway Bay on 

 the west, with hardly a portion of it attaining to an elevation of 

 300 feet above the sea, over a tract of coimtry nearly 150 miles 

 in extent in almost every direction. 



The boundaries of this great plain and those of the carboni- 

 ferous limestone almost coincide, so that we have here the some- 

 what remarkable feature of a formation which in England is of 

 such a character as to have received the name of the mountaiii 

 limestone, constituting in the neighbouring island nearly the 

 whole of the plain country. In some of the north-westera 



