To bear the load of heavy engines run at high speeds, a much stronger and heavier road was found necessary; and shortly after the opening of the Liverpool and Manchester line, it was entirely relaid with stronger materials. Now that express passenger-engines are from thirty to thirty-five tons each, the weight of the rails has been increased from 35 lbs. to 75 lbs. or 86 lbs. to the yard. Stone blocks have given place to wooden sleepers; rails with loose ends resting on the chairs, to rails with their ends firmly "fished" together; and in many places, where the traffic is unusually heavy, iron rails have been replaced by those of steel. And now see the enormous magnitude to which railway passenger-traffic has grown. In the year 1866, 274,293,668 passengers were carried by day tickets in Great Britain alone. But this was not all; for in that year 110,227 periodical tickets were issued by the different railways; and assuming half of them to be annual, one fourth half-yearly, and the remainder quarterly tickets, and that their holders made only five journeys each way weekly, this would give an additional number of 39,405,600 journeys, or a total of 313,699,268 passengers carried in Great Britain in one year. It is difficult to grasp the idea of the enormous number of persons represented by these figures. The mind is merely bewildered by them, and can form no adequate notion of their magnitude. To reckon them singly would occupy twenty years, counting at the rate of one a second for twelve hours every day. Or take another illustration. Supposing every man, woman, and child in Great Britain to make ten journeys by rail yearly, the number would fall short of the passengers carried in 1866. Mr. Porter, in his "Progress of the Nation," estimated that thirty millions of passengers, or about eighty-two thousand a day, traveled by coaches in Great Britain in 1834, an average distance of twelve miles each, at an average cost of 5_s._ a passenger, or at the rate of 5_d._ a mile; whereas above 313 millions are now carried by railway an average distance of 8-1/2 miles each, at an average cost of 1_s._ 1-1/2_d._ per passenger, or about three half-pence per mile, in considerably less than half the time. But, besides the above number of passengers, one hundred and twenty-four million tons of minerals and merchandise were carried by railway in the United Kingdom in 1866, and fifteen millions of cattle, besides mails, parcels, and other traffic. The distance run by passenger and goods trains in the year was 142,807,853 miles, to accomplish which it is estimated that four miles of railway on an average must be covered by running trains during every second all the year round.