White spruce or white fir (Abies excelsa).—The knots are small and irregularly placed, are dark in colour, and start at an obtuse angle, showing an absence of clean wood. It is used principally for scaffold poles and ladder sides. It will snap under live loads, and is not so strong as pine. It also chiefly grows in Northern Europe.
Larch (genus Larix) is imported from Northern Europe and America. It is yellow in colour, tough, and is suitable for poles, very durable, free from knots, but warps easily.
Elm (genus Ulmus) grows in the British Isles. The colour varies from the reddish-brown of the heartwood to yellowish white of the sapwood. It bears considerable pressure across the grain, and is most useful in balks, as it is liable to warp when in smaller sizes. Is suitable where bolts and nails have to be used.
Birch (Betula alba).—Light brown in colour, hard, even grain, which enables it to be easily and readily split in the direction of its length. It is not considered durable. It is used chiefly for putlogs. Is exported from Europe and America.
Ash (Fraxinus excelsior).—Very light brown in colour, extremely tough, and makes excellent rungs for ladders. It is found in Europe.
Oak (genus Quercus), also known as the common British oak, is a native of all parts of Europe, from Sweden to the Mediterranean. The wood has often a reddish tinge; and the grain is fairly straight, and splits easily. It is generally free from knots, and is most suitable where a stiff, straight-grained wood is desirable. It also offers considerable resistance to pressure across the grain.
Selection.—The importation of scaffolding timber commences in March. In June the Russian timbers are on the market, and the arrivals continue until October.
Poles are selected from spruce, pine, and larch trees. Balk timbers are of elm and fir and spruce. The putlogs are from the birch.
Poles are known in two qualities—‘prime’ and ‘brack.’ These terms refer to their straightness of grain, freedom from knots, regularity of taper, which should be slight, and condition as to seasoning.
Buyers take them usually unbarked, as they rise from the stack, and sort them afterwards for their different purposes.