466 Notices of Memoirs — British Association — Leeds. 



to be built, limestone was quarried close by in Millgill, not far from 

 Millgill Fors. The rock is a slightly- argillaceous limestone, gene- 

 rally crowded with fossils. This was roughly dressed into shape, 

 and finally chiselled along marginal fillets when the rock was built 

 up as the quoins of the station and its surrounding buildings. I 

 had occasion to stay a few hours at the station lately, and then took 

 careful note of the condition of the stone at that time. After an 

 exposure of twelve years the dressed surface of the stone in question 

 is every whei'e rough to the feel; and the general surface has been 

 lowered by atmospheric waste in the mean time to such an extent 

 that some of the more durable fragments of fossils remain in relief 

 to about a twentieth of an inch. Assuming that the upper surface 

 of the fossils represents the original dressed surface of the limestone 

 quoins, then it is evident that the limestone has already wasted 

 away at the rate of one inch in two hundred and forty years. This, 

 however, is only the beginning of it : when the weather has eaten 

 into the bedding planes and the bate of the rock, then the rate 

 of waste will certainly be proportionate to the increased surface 

 exposed to the attacks of the weather. 



We have, in these facts, some kind of measure of the initial rate 

 at which limestone is wasted along any given surface. Briefly 

 summarized the facts are these : — 



The Kirkby Stephen tombstones had weathered at the rate of 1 inch in 500 years. 

 The Tailbrig " macadam " ,, ,, 1 ,, 2-50 ,, 



The Penrith limestone „ ,, 1 „ 300 ,, 



The Askrigg limestone „ ,, 1 ,, 240 ,, 



A rough average based upon these observed facts would indicate 

 as a kind of general rate of waste about one inch in three hundred 

 years : that, of course, refers to waste along one plane, and does 

 not take into account the greatly accelerated waste consequent upon 

 the rock being attacked simultaneously along many different planes. 

 I believe we shall not err greatly in assigning at least double the 

 rate of erosion to limestone generally. 



The bearing of these facts upon some larger phenomena of denu- 

 dation will be indicated in a subsequent communication. 



itotices oif 1 zmzzezmzoi^s. 



British Association for the Advancement of Science. 



Leeds, September 4th to 10th, 1890. 



List op Titles of Papers read in Section C, Geology. 



Professor A. H. Green, M.A., F.R.S., President. 



The President's Address. (See p. 475.) 



Professor O. C. Marsh. — On the gigantic Ceratopsidce (or horned 



Dinosaurs) of North America. 

 B. Holgate. — The Carboniferous Strata of Leeds and its immediate 



Suburbs. 

 B. Holgate. — Some Physical Properties of the Coals of the Leeds 

 District. 



