(11.) Each person tendering must send to the office of the borough engineer a sample of the road metal he offers, accompanied by a full description, and the name and position of the quarry from which it is produced; such sample to be not less that one cwt. in weight, and to be retained by the corporation in the event of the tender being accepted. (12.) The corporation do not bind themselves to accept the lowest or any tender; and they further retain the right to reject a contractor in the event of his failing to find sureties to their satisfaction in compliance with the 10th condition. (13.) The word “corporation” shall mean the mayor, aldermen and burgesses, of        in their capacity as the urban sanitary authority for       . The word “contractor” shall mean the person whose tender is accepted, and who has signed these conditions; and the words “borough engineer” shall mean the engineer to the said corporation for the time being. Since writing this chapter my attention has been directed to a stone-breaking machine which is said to substitute a “knapping” for that of the usual crushing motion which is so generally the great defect in these machines: I allude to that known as “Baxter’s patent knapping-motion stone breaker,” by which a rapid jerk or blow is given instead of the slow crushing movement, thus (it is contended) causing less waste from dust and chippings, and also less strain of the machinery and less power to drive it. [26] Toughness is not all that is required. Leather would be very difficult to break with a hammer, but it would not make a good road metal. [27] I have tried this experiment, but without success, except on such soft stones as were evidently unfitted for use as a road metal. [28] Many hundreds of miles of roadways in this country are made with limestones; they often make an excellent surface, as they possess a considerable power of binding together, but weather and very heavy traffic affect them considerably: as they all have a strong affinity for water, their very power of thus cementing themselves together causes a quantity of dust in dry, and mud in wet weather. [29] A flinty or quartzose stone seems to harden with exposure. This is notably the case in pebbles; old pebble paving taken up and broken makes a most hard and durable road metal. [30] ‘Roads, Streets and Pavements,’ by Q. A. Gillmore, p. 10. [31] _Ibid._ [32] _Vide_ ‘The Maintenance of Macadamised Roadways,’ by Thomas Codrington, p. 33, a most excellent work upon this subject. [33] Mr. W. Bold considered a hammer weighing 1¹⁄₄ lb. of an elliptical form, pointed at the ends, the area of each end being about ¹⁄₁₀₀th of a square inch, to be the most suitable to break hard stones. _Vide_ ‘Minutes of Proceedings, Institution of Civil Engineers,’ vol. i. (1840) p. 50. [34] ‘The Maintenance of Macadamised Roads,’ by Thomas Codrington, p. 38.