TRANSACTIONS OP THE SECTIONS. 95 



of water. Observations -were commenced after tlie new pipe and cistern had been 

 in use for several weeks, and were continued for about a month, the water being; 

 changed eveiy twenty-four hours. The average quantity of lead dissolved in 

 twenty-four hours was 



In the old pipe ^ grain per gallon. 

 In the new pipe ^ grain per gallon. 

 In the cistern -^^ grain per gallon. 



The greater amount dissolved in the new pipe than in the cistern depends upon 

 the larger extent of surface exposed, in the one case 31, in the other only Sg square 

 feet to each cubic foot of water. 



The quantities of lead dissolved, although consideriibly below the proportions 

 considered actually dangerous, are, nevertheless, somewhat alamiing ; but it must 

 be borne in mind that the water seldom remains in the pipes more than ten hours, 

 and that during the night when the temperature is lowest ; and that in Glasgow 

 the water is usually supplied direct fi'om the street mains, without passing through 

 cisterns. 



The results obtained by Dr. Wallace may be reduced to the following simimaiy :— 

 1st, the water-supply of Glasgow is very sensibly harder, and acts with considerably 

 less energy on lead than the water of Loch Katiine ; and 2nd, the amount of lead 

 taken up from pipes and cisterns at the present time is not such as to give rise to 

 serious apprehensions. 



On an Apparatus for the rapid Separation and Measurement of Oases. 

 By Drs. Williamson and Russell. 



GEOLOGY. 



Address ly Sir Roderick Impet MuRcmsoN, D.C.L., LL.D., F.R.S., Direc- 

 tor- General of the Geoloyical Survey of the United Kingdom, President of the 

 Section. 



Although I have had the honour of presiding over the geologists of the British 

 Association at several previous Meetings since our first gathering at York, now 

 thirty years ago, I have never been called upon to open the business of this Section 

 with an address; this custom having been introduced since I last occupied the 

 geological chair at Glasgow, in 1865. 



The addresses of my immediate predecessors, and the last anniversary discourse 

 of the President of the Geological Society of London, have embraced so much of 

 the recent progress of our science in many branthes, that it would be superfluous 

 on my part to go over many topics again which have been already well treated. 



Thus, it is needless that I should occupy your time by alluding to the engi'ossino- 

 subject of the most recent natural operations with which the geologist has to deal and 

 which connect his labours with those of the ethnologist. On this head I will oulv 

 say that, having carefully examined the detrital accumulations formino- the ancient 

 banks of the river Somme in France, I am as complete a believer in the commix- 

 ture in that ancient alluviimi of the works of man with the reliquise of extinct ani- 

 mals, as their meritorious discoverer, M. Boucher de Perthes, or as their expounders 

 Prestwich, Lyell, and others. I may, however, express my gratification in learn- 

 ing that our own countiy is now affording proofs of similar intermixture both in 

 Bedfordshire, Lincolnshire, and other counties ; and, possibly, at this Meetino- we 

 may have to record additional evidences on this highly interesting topic. " 



But I pass at once from any consideration of these recent accunudations, and, 

 indeed, of all tertiary rocks ; and, as a brief space of time only is at my disposal I 

 will now merely lay before you a concise retrospect of the progress wliich has latterly 

 been made in the development of one great branch of oui- science. I confine myself 

 then to the consideration of those primeval rocks with which my own reseitrches 

 have for many years been most connected, with a few allusioua only to metamor- 

 phism, and certain metalliferous productions^ &c. 



