CIVIL ENGINEERING PRACTICE.

CHAPTER I.

ORDNANCE MAPS.

THE first and most prominent objects in a Civil Engineer's office are his maps, and a few words on these important accessories will therefore not be out of place as an introduction to what is to follow.

It is absolutely essential to every engineer, surveyor, and estate agent to have good and reliable maps of the particular districts with which he is concerned, as when once these are provided, accurate and up-to-date in every detail, they become an engineer's most valued aid. They save him time and money, and are of the utmost assistance in legal cases.

Maps of estates should be coloured to show the different holdings, each holding being carefully numbered and referred to in a schedule, where the fullest information, which it would be impossible to print on the map itself, is given. For town and country work they should have all watercourses carefully marked; all sewers, drains, water and gas mains, fountains, electric cables and public conveniences very carefully indicated; in fact, all possible information which a surveyor has handy should be neatly entered thereon, various colours, properly used, being of the utmost assistance in accomplishing this.

These maps may be the results of extensive surveys which have taken years to complete, or they may have been plotted from various sources, such as old maps, which were made with remarkable accuracy considering the disadvantages under which surveyors laboured in olden days, but in an up-to-date British engineer's office they are usually what are termed Ordnance maps. These Ordnance maps are the result of the Ordnance Survey of Great Britain and Ireland, first undertaken by the Royal Engineers* in 1747, intended for military purposes, but now carried on by the Board of Agriculture and Fisheries. These maps are marvels of accuracy and cheapness. They are on sale in most towns, but the head offices are at Southampton and Dublin, and the price varies from d. per sheet upwards, according to size and district.

The scales upon which they are printed are

63365, or 1 inch to 1 mile.

1 or 6 inches to 1 mile.

105609

1

2500, or 25 inches to 1 mile.

See White's Ordnance Survey of the United Kingdom, 1886.