98 Mr. Gilbert on Wheels for Carriages. 



square of its height; and a still further force, many times greater 

 than the former when the velocity is considerable, to overcome the 

 inertia, and this increases with the height of the obstacle, and with 

 the rapidity of the motion, both squared. But, when springs are 

 used, this latter part, by far the most important, almost entirely 

 disappears, and their beneficial effects in obviating the injuries of 

 percussion are proportionate also to the velocities squared. 



The advantages consequent to the draft from suspending heavy 

 baggage on the springs, were first generally perceived about 40 years 

 since on the introduction of mail-coaches ; then baskets and boots 

 were removed, and their contents were heaped on the top of the 

 carriage. The accidental circumstance, however, of the height being 

 thus placed at a considerable elevation, gave occasion to a pre- 

 judice, the cause of innumerable accidents, and which has not, up 

 to the present time, entirely lost its influence ; yet, a moment's 

 consideration must be sufficient to convince any one, that when 

 the body of a carriage is attached to certain given points, no other 

 effect can possibly be produced by raising or by depressing the 

 Aveights within it, than to create a greater or a less tendency to 

 overturn. 



The extensive use of waggons suspended on springs, for con- 

 veying heavy articles, introdiced within these two or three last 

 years, will form an epoch in the history of internal land commu- 

 nication, not much inferior perhaps in importance to that when 

 mail-coaches were first adopted; and the extension of vans in so 

 short a time to places the most remote from the metropolis, 

 induces a hope and expectation, that as roads improve the means 

 of preserving them will improve also, possibly ip an equal degree, 

 so that permanence and consequent cheapness, in addition to faci- 

 lity of conveyance, will be distinguished features of the M'Adam 

 system. 



