840 



PEACTICAL GEOLOaY. 



OH THE PRACTICAL APPLICATION OF GEOLOGY TO CERTAIN DEPARTMENTS OP 

 EAILWAT-ENGINEERING, WITH A DESCRIPTION OF A METHOD OF MAKING 

 WORKING-MODELS. 



By T. E. Ccrley, C.E., F.G.S., A. Ins. C.E. 



Sir,— Although the following is not purely geological, perhaps you 

 will not consider it inadmissible in your journal, as it tends to illustrate 

 a system of making geological models and sections of large tracts of 

 country for engineering-purposes. 



It is a well-known fact that hundreds of thousands of pounds might 

 have been saved in the construction of our railways, if time had been 

 taken to study in detail the geology of the country traversed, instead, 

 as was the case in 1844 and 45, of laying down the projected lines 

 on the ordnance map from the nearest turnpike-road, when travelling 

 at the rate of eight or ten miles an hour, or even, as was very often 

 done, in the office, without seeing the ground at all. Innumerable 

 slips, wet cuttings, wet tunnels, ko., might have been avoided by a 

 slight diversion, based on geological knowledge. For instance, take 

 a line running along a narrow gorge of some small river or stream in 

 a northerly direction, and suppose the rocks on each side to have the 

 same dip from west to east. J^ow, if the railway be made on the west 

 side, in side-cutting it is obvious there will be slips, if the angle of 

 inclination of the strata is greater than the angle of repose ; and cer- 

 tain that the cutting will be a wet one, requiring a flat slope, and in- 

 volving expensive drainage ; whereas, if the railway was projected on 

 the opposite or east side of the gorge, it is highly probable that the 

 cutting would be perfectly dry, and that the slope would stand nearly 

 perpendicular. 



In 1843, the Leeds and Thirsk Hallway Company projected a tunnel 

 through the Bramhope Hills, from which issue the springs and streams 

 that partly supply the Eccup Beservoir, belonging to the Leeds 

 "Water Works Company. In 1845, Mr. Seather, of Leeds, the engineer 

 for that company, instructed me to make a model of the portion of 

 country lying between Eccup Beservoir and Otley, for the purpose of 

 illustrating the geological and engineering evidence required in 

 opposing the railway-bill before the Committees of both Houses of Par- 

 liament ; and by which we succeeded in getting a clause introduced 

 for compensating the Water Company for any loss of water they should 

 sustain through the rail way- works. 



The following is the plan I adopted in making the model, which 

 embraced about twenty square-miles of country. In the first place, I 

 made a ground-plan showing the principal roads, streams, springs, &c. ; 

 I next took cross sections of the range of hills, twenty chains apart, and 

 parallel to each other ; also, a longitudinal section through the centre, 

 at right angles to the line of strike of the rocks, as well as to the cross 

 sections. 



