14 



breadths, 5J yards in length. The breadths in all cases are 27 

 inches in width. 



A circle of gas-pipe is used to keep the mouth of each tent 

 expanded. The circle is made in halves ; the ends are joined by 

 short pieces of larger pipe into which they slip and are held in place 

 by loosely-fitting bolts passing through holes drilled through both 

 the end of the circle and the short connecting piece. Before the 

 ends are connected the halves are attached to the tent by passing 

 them through iron rings sewn to the tent about one foot from the 

 bottom. These rings fit loosely. On all but the smallest tents, one 

 is attached at each seam; the smallest tents have three to each 

 two breadths. It would have been better to have used three to each 

 two breadths on all the tents ; the cloth should be reinforced where 

 they are attached. 



A stout pole ending in a U-shaped iron rest is used to support the 

 crowns of the larger tents in placing them over and in removing 

 them from the trees; the rest is hooked in the rope loops. 



The Sheets. The sheets are made in the form of a regular 

 octagon. They are six in number, and vary from 32 to 48 feet 

 across. Widths of cloth from 27 inches to 10 feet were used in the 

 construction of different sheets, but it was found most economical to 

 use the narrowest width, the additional expense for sewing being less 

 than the relatively greater value of the cloth. Ten-ounce duck was 

 used for the middle breadths of equal length, and eight-ounce duck 

 for the breadths outside of these. It is not believed that the heavier 

 cloth added sufficient to the strength to make its use desirable, and 

 if other sheets were now to be made, eight-ounce duck throughout 

 would be employed. 



In cutting the cloth to secure the octagonal shape, little trouble 

 will be experienced if it is remembered that one side of a regular 

 octagon is equal to about five-twelfths of the total length, and that 

 each breadth will be its own width shorter outside than the breadth 

 next to it toward the middle. For instance, in an octagonal sheet 54 

 feet across made from cloth 27 inches wide, the ten middle breadths 

 are the full length of 54 feet, the next breadth on each side is 54 

 feet on the inside and twice its own width or 4| feet less than 54 

 feet on the outside. By cutting the breadth for the two sides 

 alternately there will be only one mitre of cloth wasted. 



Both sheets and tents were sewed by machine with heavy linen 

 thread (principally Barber's No. 35) . The seams in the tents were 

 run down once only, while those in the sheets were turned over and 

 sewed a second time, as the strain on the cloth is much greater in the 

 sheets than in the tents. 



Oiling of the Cloth. To make the tents and sheets impervious 

 to the gas, the cloth after being made up was brushed with a 

 mixture of four parts of boiled linseed oil to one part of turpentine. 



