As reported by Stutterheim1 certain aggregates in South Africa cause very large dimensional changes in mortar and concrete. There appears to be some uncertainty as to the most desirable course of action to be taken when a particular aggregate from the area in which shrinking aggregates occur, or when an aggregate from outside this area which may be suspect from this point of view, is being considered for use in concrete or mortar.
The paper descriptionbes a method of locating leaks in a pressure pipe-line based on a mathematical analysis of leakage rates. The field procedure and the practical application of the method are discussed.
Artificial formation fracturing of rock formations to increase petroleum yield from boreholes has recently become a widely employed procedure in the United States. The author has adapted the principles of the treatment to effect increased water production from boreholes in South Africa. In this paper, the method of fracturing and results of the treatment are briefly discussed.
The paper was a condensed account of portion of the important work which had been carried out for several years in the Chief Civil Engineer's Office of the South African Railways on improvements of speed and safety of trains and the comfort of passengers. The Author had played a leading part in these investigations, and members might be interested to learn that most of the designs to which attention was drawn had been accepted as new standards on the South African Railways.
The analysis of coats of aerial surveys given by Mr Baumann in his valuable and informative paper did not seem to be complete in that no allowance appeared to have been made for general overhead expenses, such as salaries of professional and other staff at head office engaged in organisation of the surveys, cost and maintenance of buildings, housing the staff and plotters, interest on capital invested in equipment, etc. Private enterprise had to take these into account and a true picture of costs could not he given without them.
A characteristic feature of the engineering type of survey is that the accuracy requirements vary widely between fine and coarse from survey to survey, depending on the purpose behind each survey. In cadastral surveying great accuracy of horizontal position is important to the exclusion of almost everything else, but in engineering surveys vertical accuracy is the more important in practically every case where aerial survey is applicable, that is in practically every stage of design up to the penultimate one. For this reason the stress is usually laid on a uniformly dependable accuracy of contours and faithful depiction of topography, and horizontal accuracy is usually a function of the allowable plotting errors.