GOOD AND BAD EOADS. 69 



York are comparatively valueless, because the roads among 

 the mountains are so few and so bad, that the expense of 

 the transportation of the metal would exceed its value. 

 So, too, in Spain it has been known, after a succession of 

 abundant harvests, that the wheat has actually been 

 allowed to rot, because it wo-uld not repay the cost of 

 carriage." Again, " When the Spanish government re- 

 quired a supply of grain to be transferred from Old Castile 

 to Madrid, 30,000 horses and mules were necessary for the 

 transportation of four hundred and eighty tons of wheat. 

 Upon a broken-stone road of the best sort, one-hundredth 

 of that number could easily have done the work." He 

 furthiir adds, in speaking of the improvements in roads 

 made by Marshal Wade, in the Scottish Highlands, " His 

 military road is said to have done more for the civilization 

 of tlie Highlands than the preceding efforts of all the 

 British monarchs. But the later roads, under the more 

 scientific direction of Telford, produced a change in the 

 state of the people which is probably unparalleled in the 

 history of any country for the same space of time. Large 

 crops of wheat now cover former wastes ; farmers' houses 

 and herds of cattle are now seen where was previously a 

 desert ; estates have increased seven-fold in value and 

 annual returns; and the country has been advanced at 

 least one hundred years." 



THE WEDGE. 



The wedge is a double inclined plane, the power being 

 ai)pliod at the back to urge it forward. It becomes more 

 and more powerful as it is made more acute ; but, on ac- 

 count of the enormous amount of friction, its exact power 

 can not be very accurately estimated. It is nearly always 

 urged by successive blows of a heavy body, the momentum 

 of which imparts to it great force. 



All cutting and piercing instruments, as knives, scissors, 



