298 



THE GEOLOGIST. 



sudden increase of width at certain "beds, as tliongli the substance of 

 such strata Avas easier removed than that of others. Indeed, the 

 unequally worn surface of the limestone composing the sides of the 

 pipes seems indicative of the same thing ; for, on removing the 

 internal core of sand or clay, and so exposing this sui^face, it is inva- 

 riably found, so far as I have examined, to be unevenly worn, some 

 beds, or portions of beds, standing out in relief, and others being 

 deeply corroded all round the circumference. The widest pipe I have 

 seen was about two feet across, but most of them are u.nder twelve 

 inches. Transverse sections are usually more or less circular, oval, 

 or ovate, the diameter of course varying in different directions. 



Though, perhaps, the most of the pipes are excavated straight into 

 the limestone, yet several are more or less oblique. The most 

 remarkable instances of this kind are represented in fig. 4. In more 

 than one instance I have actually seen pipes which change the direction 

 of their original com-se, so as to become in a measuj^e slightly angiilated. 

 I cannot but think that the direction of both the latter pipes and those 

 whose courses are oblique must have been determined by some pre- 

 existing fissure or other weakness in the limestone, though in these 

 instances I have seen no indication of any such fissures. 



The pipes are usually filled with sand from the bed overlying the 

 limestone, but sometimes with sand and clay ; and occasionally a 

 great portion of the core is composed altogether of clay of an unc- 

 tuous and tenacious character, and which often contains numerous 

 remains of small vegetable roots, or the perforations once occupied 

 by such roots ; in fact, so thoroughly perforated are the cores of clay 

 sometimes by the minute ramifications of these roots, that I almost 

 believe that they would be quite pervious to water in spite of the 

 impermeable nature of the clay composing them. 



(To he continued.) 



BRITISH ASSOCIATIOiSr MEETIjS^G. 



TuR Meeting of the British Association opened on tlie 27tli of June, at Oxford, 

 nnder llie presidency of Lord "Wrotteslej. 



The President, in his address, offered some admirable remarks on astronomical 

 matters, and on the progress made in chemical science. On geology his re- 

 marks AV(>ro cliieHy confmcd to tlie interesting to]Hcs of the earheVt human 

 remams, assnoialcd with those of extinct mammalia. lYe give this part of his 

 address entire. 



"The bearing; of some recent geological discoveries on the great question of 

 the Ingh antiquity of man was bronght before your notice at your last meetins;, 

 at Aberdeen, by Sir Charles Lyelf in his opeuins- address "to the Geological 

 S-clion Smcc that time many Trench and English naturalists have visited^ the 

 valley of the Somme \\\ Tica' dv. and confirmed the opinion recently pubhshed 

 by M. Boucher de Perllu>s, in lSf7, and afterwards confirmed by Mr. Prest- 

 vieh, Sir C. Lycll, and other geologists, from personal examination of that 



