Page:Popular Science Monthly Volume 7.djvu/98

88 a high degree, so that horses and drivers ever seek it, if it is "laid intelligently by practised bands, with a low crown" or flat profile.

A low crown is practicable because there are no surface-obstacles to drainage. It is also needful to prevent horses from falling on any spaces with a heavy decline toward the gutter. What is essential for the transverse profile of these streets is no less essential for their longitudinal profile: they must have easy grades—say a pitch of less than two per cent.—since the momentum of inertia of the masses in motion enters the problem. The smooth surface intensifies the downward motion of the wheels while decreasing the friction of the hoofs of the horse, which furnishes the power of resistance against the downward motion of the vehicle, or serves for affixing the power necessary to move the vehicle up-hill. With these precautions relief is afforded to the horse, this faithful companion of man, which, being dumb, is so often brutally ill-treated and abused.

It would lead too far to enlarge upon the numerous official experiments and observations made in Paris and London by which, though made under circumstances most unfavorable for the new pavements, the proportion of accidents to horses and vehicles has been shown to be considerably less on the asphalt than on stone pavements, except in the rare case of a muddy street during wet weather. Ordinary care can achieve much, in that direction. When driving on to an isolated asphaltum road, to which, in wet weather, mud has been dragged from adjoining streets of old construction, the change ought to be managed by checking the horses and gradually returning to full speed. As, by degrees, the regeneration of the streets becomes general, this temporary precaution will become unnecessary. Allusion to these minor details was deemed à propos, since the human mind is so constituted that little is generally thought of accidents of daily occurrence, while we are apt to be severe and even unjust against novel improvements, which, of course, in the beginning present more or less difficulties to be overcome under actual tests. The same man who unconcernedly sees a horse fall on a stone-paved street, or blames the driver, and even the horse itself, regardless of the pavement, might be loud with complaints or fears about the falling of a horse if traveling on a road of new construction.

During the careful examinations as to the merits of the new pavement, questions were raised regarding its fire-proof qualities. Indeed, we hear that, during the siege of Paris by the Germans, the population, visited by cold, and short of fuel, tore up the asphaltum roads to enjoy fires fed therewith. But, on the other hand, it is also recorded that, during the eventful time of the Commune, when incendiarism was frequent and ingenious, these pavements never caught or spread the fire, the proportion of the combustibles to the incombustibles in the asphaltum of the streets being too small to feed the fire. The matter-of-fact people of London were not satisfied with any thing