in respect of magnification, field of view, and clearness of vision,
in proportion to its length. On the other hand advantage may
be taken of its length to obtain high command with comparative
security, or increased security with low command. Further,
with suitable mountings, it can be used as an instrument of
precision in conjunction with map and compass. Provision
should always be made to give bullet-proof protection to the
periscope when in use, and to allow of its being lowered for clean-
ing and safety when not in use.
It was sometimes necessary to construct machine-gun em- placements for defence in positions that either were, or might be, exposed to direct view. In certain cases the emplacement was incorporated in some existing ruin, parapet, or such-like pro- tection, where it was only necessary to conceal the embrasure. This was effected by the use of gauze painted to resemble the exterior, either in a hinged frame which could be removed for action, or fixed and fired through when need arose.
In other cases the emplacement was in the open. In such circumstances full precautions had to be taken to guard against detection by the camera also. An additional danger lay in the risk of detection from low-flying aeroplanes. To meet this a movable cover was evolved, in the nature of a lid, suitably disguised to resemble the surroundings (see figs. 4 and 5). Nor- mally this lid reposed on the top of the emplacement, overlapping it considerably; in action the lid could be raised vertically a foot or two, still affording protection against view from overhead, and also, to a partial extent, against long-distance direct view.
As a general rule, the screening of roads from observation by the enemy is not in the province of camouflage, in that no deception is attempted, the main object being to conceal traffic from direct view.
In a few instances true camouflage was practised when a screen painted to represent the enemy's accustomed view of the locality was erected between the road and the enemy, so that the road would always appear unused even while traffic was passing behind the screen. Such an expedient was restricted to a few favourable places, such as occasional gaps in a road otherwise entirely hidden from view, or open spaces in a village where the ruins for the most part obstructed the enemy's vision. These screens were impracti- cable in cases where the portions to be concealed exceeded a few yards in length, as they were exposed to the weather and casual shelling, and therefore had to be very strongly constructed. This, combined with the necessity of complete erection at night and the fact that they could be used only where the locality was not subject to marked seasonal changes, considerably limited their use.
(3) Miscellaneous Applications of Camouflage. It was only natural that, after a camouflage unit had been organized, with skilled personnel and well-equipped workshops, there was a wide field for the display of ingenuity. For the most part the field has been covered in the fowgoing sections dealing with the methods of combating air and ground observation, but it will be of in- terest to give a short description of devices that fall outside these two categories.
Dummy Attacks. In 1917 the practice of raiding the enemy trenches increased in frequency and scale, and in order to secure the best results with the least expenditure of life, dummy attacks were frequently staged on the flanks of the real front of attack, and set in motion a few moments before it. The dummy (or " Chinese " as it was called) attack consisted of numbers of life- sized silhouette figures, made of stout millboard and painted to resemble the various postures of advancing troops. These figures were placed in scattered groups of ten, and suitable arrange- ments made to raise and lower them at will from some place of safety, so that they simulated waves of advancing troops (see fig. 7). In the early light of dawn, or partially obscured by smoke, they were very realistic, but success depends on skilful operation of the figures rather than on the painting. Directly the enemy's fire was drawn the real attack was launched with the comforting knowledge that many precious moments must elapse before the enemy could switch his fire off the dummy at- tack on to the real attack.
Similarly, the location of enemy snipers was facilitated by the use of dummy heads made of papier-mache. These were exposed over the parapet, in a life-like manner, in order to draw the fire of an enemy sniper. If the head was hit, it was possible to locate the exact position of the sniper by producing the alignment of the
holes of entry and exit of the bullet. It was necessary to paint these heads with a matt surface, darker in tone than the natural, in order to imitate the texture of the human face.
Sniper Suits. The concealment of snipers and scouts was facilitated by the wearing of costumes painted to match the surroundings. When garnished with local vegetation, and used skilfully, it was extremely difficult to discover the wearer. Fig. 8 shows an exceptionally tall man lying quite in the open, but wearing a sniper's robe. Fig. 9 shows, in contrast, two men firing from behind a turnip heap, the one wearing the ordinary uniform cap and the other a sniper's robe suitably garnished. In each case the photographs were taken at a distance of only 8 yds.
Disruptive painting, as a method of reducing visibility, has been alluded to in an earlier section of this article. Its simplicity makes a strong appeal to the imagination, and a large number of objects, including guns, were so treated. The colours employed were green, cream and brown, isolated from each other by thick black lines. The principle is that one or more of these colours is capable of merging into any surroundings, leaving the visible remainder as a number of detached patches of colour, thus breaking up the form of the object into a number of dissociated pieces. The contrasts in colour must be marked, and the patches large enough to be distinct when viewed from the appropriate distance; otherwise the colours will blend and, in consequence, the disruptive effect will be lost. An effect of texture is also essential to prevent reflection. In the case of guns, it was soon found that the wear and tear of active service caused the colours to lose their contrast and, consequently, their disruptive effect. The system was therefore abandoned.
In the case of large buildings and camps, the disruptive effect is nullified by their mass, heavy shadows and quite inevitable regularity of lay-out.
Camouflage Material and Its Production. By no means the least difficult part of the whole problem of camouflage was that of pro- ducing the material in sufficient quantities to meet the enormous demands. At first each position was treated individually as a separ- ate problem, but it was very soon obvious that although this princi- ple was desirable it was quite impossible, in view of the number of positions to be dealt with. It was evident that a system of standard- ization was imperative, in conjunction with some method of adapt- ing the general to the particular. Standardized manufacture was therefore adopted. It was recognized that in certain cases stand- ardization could not be applied; but experience showed that the proportion of such cases was small. In all cases the material was capable of some degree of adaptation to local conditions.
For gun positions, etc., three distinct media were furnished fish nets, wire netting and scrim.
Fish Nets. -The nets themselves were supplied from England. The size, 30 ft. by 30 ft., was fixed as being the minimum suitable for universal application; one or more nets could be easily joined if necessary. The nets were woven "square" in contradistinction to "diagonal," because the diagonal net closes when extended, cf. the principle of " lazy tongs." The meshes were 2j in. square. The outside was bound with strong cord to take the tension, and the whole was treated with a non-inflammable preservative. The gar- nishing of these nets has already been described. The nets were commonly used for all types of guns and were in demand because of their comparative portability.
Wire Netting was used in large quantities also, being stronger than fish netting, though less portable. For convenience in handling it was made up in rolls 30 ft. long, averaging 6 ft. wide, and was garnished in a fashion similar to fish netting, except that the thin- ning process could only be applied to the ends. In the field these rolls were joined up to suit the work they were intended to cover, and the thinning-out process was completed on the site.
Scrim, as already mentioned, by itself was mainly used on or near the ground and was issued in 30 ft. by 6 ft. rolls for a variety of purposes. Towards the end of the war, when night bombing became very persistent, scrim was used to cover aeroplane hangars (whose light-coloured roofs were very conspicuous at night), until cfoloured covers became the normal equipment of a hangar.
Colouration. In these three types four standard colourations were adopted, suited respectively to areas where the predominant conditions were: all vegetation, all earth, partly earth and mostly vegetation, partly vegetation and mostly earth. Both the scrim centres and the borders of strips were coloured in this way.
Observation Posts, etc. Standardization of the exteriors of observa- tion posts was not possible for obvious reasons, but the principle was applied to the bullet-proof interiors and other component parts. They were classified as: observer trees, periscope trees, parapets (sandbag or earth), portable O.P.'s. In addition there were many
