The kind of rails to be laid down to form the permanent road was a matter of considerable importance. A wooden tram-road had been contemplated when the first act was applied for; but Stephenson having advised that an iron road should be laid down, he was instructed to draw up a specification of the rails. He went before the directors to discuss with them the kind of material to be specified. He was himself interested in the patent for cast-iron rails, which he had taken out in conjunction with Mr. Losh in 1816, and, of course, it was to his interest that his articles should be used. But when requested to give his opinion on the subject, he frankly said to the directors, "Well, gentlemen, to tell you the truth, although it would put £500 in my pocket to specify my own patent rails, I can not do so after the experience I have had. If you take my advice, you will not lay down a single cast-iron rail." "Why?" asked the directors. "Because they will not stand the weight, and you will be at no end of expense for repairs and relays." "What kind of road, then," he was asked, "would you recommend?" "Malleable rails, certainly," said he; "and I can recommend them with the more confidence from the fact that at Killingworth we have had some Swedish bars laid down--nailed to wooden sleepers--for a period of fourteen years, the wagons passing over them daily, and there they are, in use yet, whereas the cast rails are constantly giving way."[55] The price of malleable rails was, however, so high--being then worth about £12 per ton as compared with cast-iron rails at about £5 10_s._--and the saving of expense was so important a consideration with the subscribers, that Stephenson was directed to provide in the specification that only one half of the rails required--or about 800 tons--should be of malleable iron, and the remainder of cast iron. The malleable rails were of the kind called "fish-bellied," and weighed 28 lbs. to the yard, being 2-1/4 inches broad at the top, with the upper flange 3/4 inch thick. They were only 2 inches in depth at the points at which they rested on the chairs, and 3-1/4 inches in the middle or bellied part.