During the twelfth century the helmet gradually became the helm. The ear-flaps were fixed, becoming an integral part of the defence, and closed round to join the nasal, this arrangement forming at length the ventail or visor. This gives us what is known as the 'Barrel helm' (Fig. 2), in which the whole head is enclosed and the only opening in the front is the 'ocularium' or vision slit. Next we have the same kind of helm with the addition of holes for breathing in the lower portion (Fig. 3). In some varieties the back of the helm is shorter than the front, as on Fig. 4, and in this kind also we sometimes find breathing holes added. The Great Seals of the kings are a most useful guide in discovering the accoutrements of each period, and especially so for the helms and helmets, which are easier to distinguish than the more minute details of dress and equipment. It will be understood that in time the flat-topped helm was given up in favour of the 'Sugar-loaf' helm (Fig. 5), as it is generally called, when we consider the importance of a 'glancing surface' in armour. Although thickness of material was of some importance in defensive armour, this providing of surfaces from which a weapon would slip was considered to be of supreme importance by the armour-smiths of later periods. In the conical helm, as indeed in nearly all great helms, the vision and breathing apertures were pierced in the plates of the helm itself and were not part of a movable visor, as was the case in the helmet. The weight of these helms must have been great; for they do not seem to have been bolted on to the shoulders, as were the fifteenth and sixteenth century tilting helms, but to have rested upon the crown of the head. The drawing on Plate I, No. 8, shows a padded cap which was worn under the mail to protect the head from pressure. On No. 12 of the same plate we see the helm being put on over the mail coif; the padded cap is worn under the mail. For tournaments the helm was sometimes made of toughened leather, which was called 'cuirbouilli' from the fact that it was prepared by being boiled in oil and then moulded to shape. This material was very strong and serviceable and was used, as we shall see later on, for reinforcing the chain armour and also for horse armour. It was generally decorated with gilding and painting. For the tournament held at Windsor in 1278 we find mention of 'xxxviii galee de cor'.[8] As we have shown, these great helms were not attached to the body armour and were thus liable to be struck off in battle. In order to recover them a chain was sometimes stapled to the helm and fastened to the waist or some portion of the body armour (Fig. 6).