108 PRESSURE OF AIR. 



the surfaces of all things, the bricklayer would need 

 no mortar, the joiner no nail and no glue ; the tailor, 

 too, would have no use for thread, and the seams 

 of shoes would never give way. A world of that 

 kind would be a very stable and lasting world, and 

 the words " wear and tear" might be left out of the 

 vocabulary. But there would be too much of sta- 

 bility ; and there would be little motion, or change, 

 and no life. 



Thus the extreme pureness of the atmosphere, 

 and the property that it has of insinuating itself into 

 the very smallest openings, and pressing equally in 

 all directions, makes it the grand pathway on land ; 

 for whatever is moved on land is literally moved in 

 the air ; and not only that, but, as the air is pressed 

 together by its own weight, and thus heaviest near* 

 est the earth, so that even the heaviest substances 

 are pressed a little more upward than they are 

 pressed downward by the air, their real weights 

 are diminished by the weight of a quantity of air equal 

 to their bulk. At the same time, they are held in 

 their upright position by the pressure of the air all 

 around them ; and that pressure is so considerable 

 as to amount to about thirteen tuns on the body of a 

 man. That weight is, however, so nicely balanced, 

 so perfectly the same at all points of the same ele- 

 vation from the ground, and the air is so perfectly 

 springy or elastic, forms so delightfully soft a 

 cushion around all nature, that its resistance to ordi- 

 nary motions is not felt, and it does not ruffle the 

 powdery plumage on the wing of the most delicate 

 moth. Walking we do not feel it at all ; and even 

 when we run with all our speed, it is nothing but a 

 light zephyr in our face, which fans and cools us, 

 and really assists in speeding us on. 



And it is worthy of remark how the natural cov- 

 erings of many animals are " fined away" at their 

 extremities, till they glide almost into the thinness 

 of the air itself. Take an entire hair of any animal, 



