586 SCIENTIFIC NOTICES. 



instructing his hearers upon the nature and extent of the mountain-chains 

 and highlands which stretch across the projected lines,— the geological struc- 

 ture of the strata to be worked by the engineer,— and the nature of the levels 

 and water- courses by which they are drained, — the lecturer appeared before 

 the members of the Institution above mentioned, which can boast of the 

 names of many scientific and highly gifted men ; and his hearers can testify 

 to the practical value of his remarks and the interesting nature of his in- 

 formation. 



The first lecture had for its subject, A general view of the comparative 

 advantages to the country of railroad communication and the probabilities 

 of gain to the shareholders. The drainage of England by the five great basins 

 of the Humber, Wash, Thames, Severn, and Mersey was next considered 

 and described in detail, in connection with the various artificial lines of 

 water-communication connecting them. The Humber drains a tract of 

 country equal to 9000 square miles ; the rivers of the Wash 5000 ; the 

 Thames 5,500; and the Severn 4500. The Mersey, compared with the 

 preceding, is of minor extent and drainage ; but, owing to the number of 

 manufacturing towns on its tributaries and its numerous canal connections, 

 it has a claim to a full consideration among the great basins of England. 



In his second lecture Mr. Davis described the great mountain chains and 

 highlands which cross England in diflferent directions, and explained the in- 

 clination of the watersheds and the convergence of the streams belonging to 

 the difi'erent systems in the great recipient basins. The extreme height at 

 various points of these chains was thought to be of the greatest interest to 

 all persons connected with railroads, and especially to the engineers em- 

 ployed in their construction ; and no better illustration of these elevations 

 could easily be given than that derived from the knowledge of the canal-levels. 

 On canals it would be found that, when the elevation was moderate, it was 

 practicable to raise the canal by means of locks ; in other instances, of greater 

 weight, a tunnel carried through the rocks became necessary ; and again, 

 when the level was suddenly broken by a deep valley or by the channel of a 

 watercourse, an aqueduct or embankment was constructed. 



In excavating a tunnel, a knowledge of the nature of the strata to be 

 worked through was of paramount importance ; for, should the soil be loose, 

 it must first be cut with great expense and risk of life, and be permanently 

 supported by an interior architecture, while in the more compact strata the 

 solidity of the stone alone was found to be a sufficient security. Instances 

 of tunnels cut through the solid limestone rock were not unfrequent. In one 

 canal (the Thames and Severn) the tunnel is upwards of a mile in length, 

 with no other support than the natural adhesion of the rocky particles through 

 ■which it is bored. One of the most remarkable of the canals of England is 

 the Huddersfield canal. The stream flows through a tunnel three miles in 

 length, cut directly through the lower secondary rocks and coal strata. This 

 canal falls 339 feet in nine miles. , • v r 



The natural imnediments which have been surmounted in the formation 

 of canals, and the extraordinary difficulties of very different kinds which 

 have occurred to the engineers in the progress of their works, with the expe- 

 rience which has been attained respecting the strata of England, in the busi- 

 ness of canal-engineering, are all objects for mature consideration, and 

 necessary to enter into the estimate of the advantages extracted from rail- 

 road communication. Many of the schemes at present in existence could 

 not, it was conceived, survive a day, if submitted to the strict geological 

 test'; and private individuals ought to exercise the soundest discretion, and 

 not 'too easilv hazard their money and their peace with remote hopes of 

 return in und'ertakings where nature herself points out their inexpediency 



and folly. . ■. j .i. 



The Lecturer, among other subjects of demonstration, described the pro- 

 jected line of the London and Birmingham railroad, illustrating its course 

 by the exhibition of a fine collection of specimens and fossils from the sue- 



