MECHANICS AND USEFUL ARTS. 35 



were broken down by the wind, it throwinof them into a state of 

 undulation to the extent of 4 or 5 feet. Scientific and judicious 

 bracing has been found a sufficient remedy in ordinary cases. The 

 engineer of the bridge over the Menai Straits considered the wind 

 pressure on this large tubular structure as a trifle, not more likely 

 to be felt than in a well-made chimney. Though bridges may not 

 be injured by the wind, railroad trains passing over them have 

 met with serious accidents from this cause. A train on the Mid- 

 land Railway, in France, consisting of 7 carriages, had 2 of its 

 carriages overturned, while running on a straight piece of line at 

 the rate of 20 miles an hour; the wind was north-west, nearly 

 perpendicular to the line of the route. The weight of the car was 

 7 tons, its moment of resistance 5 tons, the surface exposed to the 

 force of the wind 150 square feet, and the lateral pressure required 

 for its equilibrium 39 pounds per square foot. On the same train 

 a luggage van, weighing 7J tons, with a surface exposed of only 

 110 square feet, was not overturned, requiring a force of 62 pounds 

 to overthrow it. In case a train was running round a sharp 

 curve, with the wind blowing from the centre to the circumference 

 of the arc, this addition to the centrifugal force might cause an 

 overturn with a less high wind. — Civ. Eng. and Arch. Jour., 1868. 



ROAD-MAKING. 



The common practice of road-making in this country, says the 

 *• Railway Times," is one of waste and utter want of economy in 

 every respect. The process is something like this : the upper 

 soil is removed, and coarse gravel or broken stone supplied to 

 bring up the grade, and the road is then left to be worn down 

 smooth by passing teams and carriages. Think what a waste of 

 power is thus involved, what an immense and useless wear of ve- 

 hicles, what loss of time, and what amount of general discomfort. 

 Drainage is seldom thought of, and during the wet seasons, and 

 especially when the frost is coming out of the ground, the roads 

 are nearly impassable. The common remedy for all this is to pile 

 on more g-ravel or broken stone, and then again commences the 

 destruction of wheels. This useless tax to the owners of horses 

 and vehicles could nearly all be prevented if the roads were prop- 

 erly made, drained, and cared for. Proper drainage is the first 

 essential ; then the road dressed with gravel or stone should be 

 formed and rolled into proper form to shed water, — a very slight 

 incline to either side is all that is necessary, — and then 3^ou have a 

 road that is easy to horses, and the load is carried with half the 

 power that is expended in hauling over many of the roads in our 

 suburban towns. Less gravel or broken stone, but more care that 

 it is kept in place and smooth, is what is required. In England 

 and France they are using powerful steam rollers with beneficial 

 results. 



A London paper describes the process thus : " The road is first 

 prepared by being loosened with pickaxes, then covered with the 

 ordinary broken granite. Above this a dressing of sand is laid; 



