REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL. 359

and general observation is necessary to intelligently apply it, but also impresses every superintendent, supervisor, foreman, and individual workman that his efforts are properly and intelligently watched by the highest authority on the work, and that the records will approximately show his relative efficiency. The effect of and inspiration caused by methods of this character should largely increase the economical and efficient conduct of the work.
 The writer has dwelt on this subject rather at length, as, while these conclusions may not be strictly accurate, he considers that the experimental results of a year's work, modified by his knowledge of what can be done with improved machinery and appliances and proper methods, would at least be a guide in arriving at some approximate idea of the cost and time required to complete excavation work on the principal plans under consideration.
 ARBITRARIES.
 What are called arbitraries for the plant and appliances were intended to absorb the entire cost of the plant during the work, and it was thought more fair to add an arbitrary each month to the cost price per cubic yard than it was to add the cost of new plant or installation work into each month's costs, the idea being that the comparative cost per cubic yard each month should only include those items that affected the month's work, as new tracks, new equipment, new appliances, or other extensive installations would be in the way of benefit to the entire work, and it was considered fair to average them in in the form of arbitraries which could be increased or diminished or otherwise modified as experience should show to be proper.
 It is considered, however, that the amount provided, 6 cents, will be sufficient to cover the cost of this class of expenditures. In these cost sheets it was intended to include all the charges to which a contractor should be subjected. A large portion of the general expense, supervision, engineering, sanitation, etc., would be common to any method of carrying on the work, and would be provided for by the Commission even if the work was let by contract, except in case the entire work should be let to a syndicate and the Government relieved of a portion of the expenses of this nature. As in the original estimates a percentage has always been added to cover general expenses, supervision, engineering, and sanitation, the figures of cost have been confined to the lines indicated.
 As will be noted, the elements which go to make up the total unit cost per cubic yard are as follows, and the 2 cents added to the cost of 48 cents may be made available for additional equipment if the arbitraries allowed are not sufficient for the purpose:
 Mining. . . . ..------------------------------------------------------------------------$0.12
 Excavating and loading. .....------------------------------------------------------------.07
 Maintenance of tracks. . ...--------------------------------------------------------------. 05
 Transportation. ... ..-------------------------------------------------------------------. 10
 Dumps. . . . ..-------------------------------------------------------------------------.05
 General expenses......------------------------------------------------------------------. 03
 Arbitraries.. . . ..----------------------------------------------------------------------. 06
 Total. . . ..----------------------------------------------------------------------.48
 In round numbers. ..----------------------------------------------------------------.50
 Adding 20 per cent for contingencies.. ..--------------------------------------------------. 10
 Total estimated cost per cubic yard.. ..---------------------------------------------. 60

 Statement of rainfall at Culebra from July 1, 1904, to June 30, 1905.
 1904. Inches. 1905. Inches. July. ..-------------------------------- 6. 5 January..------------------------------1. 9
 August..------------------------------- 3.5 February. ..-----------------------------0.0
 September------- .---------------------13.6 March.--------------------------------1.2
 October..------------------------------10. 8 April................................... 2. 9
 November.----------------------------12.8 May. ..---------------------------------13.1
 December---------------------------- 1.8 June--------.-------------------------6.9
 Total ..... ..................... 75.0
 a Estimated.