TUNNELLING THEOUGH VAEIOUS STRATA. 161 



sand being almost uniformly dry tlironghont its wliolo ox- 

 tent. Although such a largo proportion of tlio tunnol was 

 left unlined, and passed by the Board of Trado Inspector in 

 that state, tho writer believes that since the lino was 

 opened, and especially since it has been worked as a joint 

 line of tho Midland and South Western Eailways, a large 

 portion of it has been lined ; before that was done, large 

 falls of sand occurred, and it was most unwise to leave such 

 a tunnel in a naked state, it being done, however, on the 

 score of economy, to which account, we fear, must be laid 

 many subsequent largo outlays on most of tho raihvays in 

 tho kingdom, many narrow escapes from serious accidents, 

 and probably many serious accidents themselves. 



Tunnels should, whore possible, have a rising gradient 

 from both ends, with the apex somewhere near tlio centre, 

 as it so greatly assists the drainage and construction, and 

 where the tunnel is driven from the ends only, and much 

 Water is met with, the saving in pumping is very consider- 

 able. No doubt in many cases this cannot be done, especi- 

 ally whore a tunnel is situated on a gradient of any length 

 and steepness, but where the gradient is slight it can, in 

 most instances, be arranged so as to approach the centre of 

 the tunnol with a rise from both ends. In addition to tho 

 extra diifioulty and cost of constructing a long tunnel on a 

 single steep gradient, there is the disadvantage of having 

 to pass tho whole of the drainage water, from the cutting 

 at one end, through tho tunnel ; and where the cutting, as 

 m many places, is of any length, through wet ground, this 

 generally means a large body of water. It generally means, 

 also, a great saving in tho time of construction, where there 

 IS a gradient from both ends, however slight that gradient 

 may be ; as, however much trouble and expense may be spent 

 m pumping machinery, there is always great trouble anl 



