506 HAILK0AD3. 



amount of labour for embankments and deep-cultings, whicli form a 

 grand item in the first outlay. 



5. The labour of cutting may be increased by two opposite condi- 

 tions of soil — extreme hardness, as in the case of crossing a stone 

 country, or extreme looseness and want of adhesive quality. Either 

 condition has been found to double and triple the expense of the na- 

 vigator's work. 



6. Particular attention should be directed to the situation of the rail- 

 line in relation to the base line on the section. All the previous work 

 may have been satisfactorily completed, and inattention to this may 

 saddle the shareholders with permanent loss. 



7. An unusual expense in construction may often be economical 

 when it is intended to diminish the permanent cost of transport. This 

 can only be ascertained by a careful examination of the slopes and 

 of the cost of engine working. 



8. A railroad, to be worked to the greatest possible advantage, 

 should be level, — every departure from a perfect level diminishes 

 speed or increases labour and wear and tear of engine. 



9. A slope of one in three hundred feet may be safely taken as 

 the maximum to be allowed, except under particular circumstances, 

 where great additional expense is to be risked by the employment of 

 assistant locomotive and stationary engines. 



10. Steep slopes are sometimes absolutely necessary, but they must 

 be short. The necessity of an assistant locomotive doubles the cost 

 of transport over every mile of such ground. 



11. Slopes of more than one in a hundred feet are inadmissible 

 on great railways, owing to the waste of power occasioned by the in- 

 creased resistance. 



12. The plans must be examined with the view of ascertaining the 

 number and degree of curves on the line. These curves may, if not 

 carefully managed, be attended with danger, where rapid locomo- 

 tives are employed. The danger of the trains slipping off the rails 

 in traversing a curve is increased in proportion to the speed. Hence 

 they should be placed on ground nearly level, and be as large as 

 possible. The radius of such a curve should not, according to Dr. 

 Lardner, be less than a mile. 



13. Tunnels of half a mile and less are not objectionable ; but, on a 

 line of road frequented by passengers, tunnels of a mile or more 

 should, if possible, be avoided; if not, they should be very spacious 

 and be well ventilated by shafts. As the unpleasant odour and other 

 inconveniences felt in passing tunnels are much increased by the in- 

 crease of power in the engine necessary for surmounting slopes, it is 

 desirable that they should be situated on levels. 



14. The expectation of yearly returns beyond eight per cent, on 

 capital advanced is not, we think, justified by any favourable circum- 

 stances, either of construction or of transpoi-t demand, even consider- 

 ing the diminished proportional cost of transport on long lines. The 

 cost of the construction and maintenance of the locomotives, and the 

 wear and tear of the rails, are causes of permanent expense, which 

 increase in a constant ratio with the tonnage and length of road; 

 and these points have not hitherto been sufficiently estimated. The 



