34 NATURAL THEOLOGY. 



There is one property, however, common, I be- 

 lieve, to all eyes, at least to all w^hich have been 

 examined,* namely, that the optic nerve enters the 



sure, including that of the atmosphere, of about 60 pounds on the 

 square incli ; while one at 4000 feet, a depth by no means consid- 

 erable, would be exposed to a piessure of about 1830 pounds upon 

 the square inch." — De La Beche, Tlieor. Geol. p. 243. 



We can therefore comprehend how it shall happen, that on the 

 foundering of a ship at sea, though its timbers part, not a spar floats 

 to the surface ; everything is swallowed up ; for, if the hull has sunk 

 to a great depth, all that is porous is penetrated with water, or com- 

 pressed, and consequently remains where it sunk. So it happened, 

 and the fact goes directly to our purpose, that when, by the en- 

 tangling of the line of the harpoon, the boat was carried down with 

 tlie whale, and, being recovered, it required two boats to keep it at 

 the surface. — Scoresby. 



We may easily conceive, therefore, the pressure which the eye 

 of the whale sustains when it dives, and why it is formed ■with the 

 provisions wliich we are about to descrilie. When we make a 

 eection of the whole eye, cutting through the cornea, the sclerotic 

 coat, which is dense as tanned leather, increases in thickness to- 

 wards the back part, and is full five times the tliickness behind, 

 that it is at the anterior part. The anterior part of the eye sustains 

 the pressure from without, and requires no additional support ; but 

 were the back part to yield, the globe would be then distended in 

 tliat direction, and the whole interior of the eye consequently suffer 

 derangement. We perceive, therefore, the necessity of the coats 

 being thus so remarkably strengthened behind. The natural ene- 

 mies of the whale are the sword-fish and the ^hark ; and it is stat- 

 ed with some show of reason, that tiiis huge creature, being with- 

 out means of defence of any kind, carries his enemies that have 

 fixed upon him to a depth of water, and consequently to a pressure, 

 which subdues them, as their bodies are not constituted for such 

 depths. It is under this instinct, that when the whale receives the 

 hajpoon, he dives to the bottom. 



♦ The eye of the seal or sea-calf, I understand, is an exception. 

 Mem. A^ad, Paris, 1710, p. 123. — Paley. 



