264 Introduction to the Study of Science 



8. In any machine you find convenient, as a sewing machine, 

 grindstone, lathe, or bicycle, show what combinations of the simple 

 lever, the roller, and the wheel and axle are made. 9. Show that 

 the roller, wheel and axle, and the crank are modified forms of the 

 lever. 



II. ROADS 



108. Roads and vehicles. As the vehicles used in trans- 

 portation are improved and multiplied, and the motive forces em- 

 ployed become increasingly those of steam, electricity, and gas, 

 the roads over which carriers must travel are necessarily im- 

 proved. In mountainous regions where trails are difficult and 

 narrow, pack animals, such as the horse, the mule, the llama, 

 or the burro, serve until traffic becomes too heavy. Then 

 wagons are introduced and trails must be changed into roads 

 or new roadways built over which wagons can move. Such 

 improvement is often slow, as may be observed to-day in many 

 rural districts where the farmers suffer yearly loss because of 

 the disproportionate expense of getting their crops to market. 

 The roads are unfit for loaded wagons and impossible for motor 

 trucks. Public interest in good roads is rapidly developing, 

 however, not only supporting, but even demanding, more and 

 better roadways; for it is realized that the expense of trans- 

 portation is borne not only by the farmers, but by the con- 

 sumers as well. 



With the rapidly increasing use of the automobile the con- 

 struction of roads has become more and more of a professional 

 engineering problem. The work is now regarded as too im- 

 portant to be left to unskilled supervision, as it was a few years 

 ago. To-day the most durable materials must be utilized and 

 the surface form must be such as to insure perfect drainage 

 and to facilitate transportation. But with the present- tenden- 

 cies in road construction we may compare the ancient Roman 

 roads, which are the most solid and durable ever constructed, 

 the Claudian Way being still in use after two thousand years 

 of service. Does your observation of recently constructed 



