656 PROCEEDINGS OF SECTION H. 



experience of the determination of M'atenvays on railways. The essen- 

 tial problems governing the correct determination of waterways had 

 not previously been adequately dealt with by the engineers of Queens- 

 land Railways, so that I felt the responsibility veiy keenly. 



I quickly saw, however, that the principal determining factors 

 of the problem were (a) area to bo drained in each particular case, 

 and (b) maximum rainfall to be expected. There are, of course, 

 other factors to be taken into account, such as porosity of the soil 

 and slope of the ground, but the principal factors are the two I have 

 es^pecially named. 



I knew sufficient of the climatic conditions of Queensland to 

 know that as a rule, and more especially in the coastal districts, 

 provision for less than 1 in. of rain per hour would be inadequate, 

 whilst it was apparent that to provide for unforeseen contingencies 

 and exceptionally heavy falls of rain it would be wise to allow some^ 

 what larger sectional areas than either the assumed maximum rain- 

 fall or the areas to be drained would indicate. 



On this basis I prepared a table showing the sectional area and 

 other dimensions of openings of various classes required to discharge 

 1 in. of rain per hour from areas of from one to one thousand acres, 

 with estimated velocities at the point of exit of from one to six 

 miles an hour when the openings were running not more than two- 

 thirds full, thus affording a margin of one-third for contingencies. 

 In order that the information contained in the table might be 

 correctly applied, I instituted the practice of having all the minor 

 watersheds traversed with prismatic compass and chain, this being 

 near enough to ascertain the areas with sufficiently close approxima- 

 tion to truth. With the help of the table I prepared in 1878, I 

 have determined the Avaterways on something like one thousand milevS 

 of- railway now in operation in Queensland, whilst the table is still 

 used by the engineers of the Railway Department of this State. 



Whether the practice of traversing watersheds is in vogue in 

 any other part of the world I cannot say, but I am in a position to 

 state positively that it was not the practice of the Railway Depart- 

 ment of New South Wales for several years after I instituted it in 

 Queensland. 



In practice I have generally assumed the velocity of discharge 

 through the openings, when running two-thirds full, at three miles an 

 hour. This is a safe velocity to take in the great majority of 

 instances that are met with in the coastal districts of Queensland. It 

 will be found that for an assumed velocity of three miles an hour 

 the sectional area of opening required is one square foot for each 

 three acres of area to be drained. For example, an area of thirty 

 acres would, as a iTile, require an opening having a sectional area of 

 10 sq. ft. ; this sectional area might be obtained under a deep 

 embankment by means of a brick, stone, or concrete circular culvert 

 of, say, 3 ft. 6 in. internal diameter, or in the case of a comparatively 

 shallow embankment by means of a 5 ft. by 2 ft. timber culvert-. 

 Although the table is confined to minor areas, it is often advisable to 

 traverse much larger basins, and I know several cases in my own 

 practice where areas of from 5,000 to 10,000 acres have been 

 traversed with distinct advantage and economy as regards the deter- 

 mination of the necessary watenvays. 



