88 THE POPULAR SCIENCE MONTHLY. 



a high degree, so that horses and drivers ever seeli it, if it is " laid in- 

 telligently by practised bands, with a low crown" or flat piofile. 



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 down- 

 ward 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 afiixing the power 

 necessary to move the vehicle up-hill. "With these precautions relief 

 is afibrded 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 experi- 

 ments 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 tempo- 

 rary precaution will become unnecessary. Allusion to these minor 

 details was deemed d 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 pave- 

 ment, questions were raised regarding its fire-proof qualities. Indeed, 

 we hear that, during the siege of Paris by the Germans, the popula- 

 tion, 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 



