If we arrange the companies according to their speed instead of their mileage, the order is: 

Average
r.a.      Miles
Great Northern.                     46      6,780
Great Western.                      46   [2]2,600
Midland.                            45      8,860
Manchester, Sheffield, and Lincoln  44      2,318
London and South-Western.           44        890
North-Western.                      43     10,400
Glasgow and South-Western.          43        920
Great Eastern.                      43      3,040
North-Eastern.                      43      2,110
Chatham and Dover.                  43        690
Caledonian.                         42      1,155
South-Eastern.                      41        940
Brighton.                           41      1,155
North British.                      31        825

  [Footnote 2:  Not reckoning mileage west of Exeter.]

EXPRESS ROUTES ARRANGED IN ORDER OF DIFFICULTY OF GRADIENTS, ETC.

  North British,
  Caledonian,
  Manch., Sheffield & Lincoln,
  Midland,
  Glasgow and South-Western,
  Chatham and Dover,
  South-Eastern,
  Great Northern,
  South-Western,
  Great Eastern,
  Brighton,
  North-Western,
  North-Eastern,
  Great Western.

LONG RUNS IN ENGLAND.

=======================================================

================
| Number of | Average |  Running
|  Trains.  |  Speed. |  Averages.
------------------------------------+-----------+---------+-

-----------
|           |  Miles. |   Miles. 
Midland.                            |     104   |    53   | 46  (5,512)
North-Western.                      |      98   |    60   | 45  (5,880)
Great Northern.                     |      49   |    73   | 50  (3,616)
Great Western.                      |      24   |    56   | 48  (1,344)
Great Eastern.                      |      24   |    56   | 42  (1,362)
Brighton.                           |      23   |    45   | 42  (1,047)
North-Eastern.                      |      20   |    56   | 44  (1,120)
South-Western.                      |      13   |    47   | 44    (615)
South-Eastern.                      |      12   |    66   | 42    (795)
Chatham and Dover.                  |       8   |    63   | 45    (504)
Caledonian.                         |       8   |    59   | 45    (476)
Glasgow and South-Western           |       8   |    58   | 44    (468)
Manchester, Sheffield, and Lincoln. |       8   |    48   | 43    (390)
North British.                      |       7   |    60   | 40    (423)
------------------------------------+-----------+---------+-

-----------
Total.                   |     406   |    58   | 45 (23,550)
============================================================

===========

From this it will be seen that the three great companies run 61 per cent. of the whole express mileage, and 62 per cent. of the whole number of long runs.