2 68 



HARDWICKE'S SCIENCE-GOSSIP. 



vision which j is made by means of which, that, while 

 water obeys the same general law as that governing all 

 other substances, that of increasing in bulk by heat, 

 and decreasing by cold, yet, at the moment of actual 

 freezing it swells and becomes light. And thus it is 

 that ice swims on water. If, on the contrary, it sank, 

 more ice would form on the top of the water of a lake, 

 or pond, or river, and it would sink also, and then in a 

 short time accumulated masses of superincumbent ice 

 would be formed, so great, that no summer's sun in this 

 country could melt them, while every creature in such 

 waters would perish, or rather, would never exist. And 

 our climate would be affected in a marked manner by the 

 omission of this other only apparently small matter, 

 namely, the inability of heat or cold to travel down- 

 wards in water as quickly as upwards. As it is, a limited 

 coating of ice, of thickness varying according to tem- 

 perature, forms on the surfaces of water, and nearly all 

 remains below it comfortably protected, because of the 

 feeble conduction of cold by the ice, till returning 

 spring. And it seems almost approaching a too great 

 presumption for a mere mortal to admire the framing of 

 the law which permits this slow travelling downwards 

 of heat in water, to compensate for the equally neces- 

 sary high specific heat, or great capacity for receiving 

 and retaining heat, which water possesses above all 

 other known substances, liquid or solid. As it is, the 

 slow downward progress of heat through water, pre- 

 vents the sun of summer from killing the plants and 

 cold-blooded animals in it. 



Sea water requires a much greater cold to freeze it 

 than fresh water does ; hence (conjoined with the 

 motion of the ocean around England and many other 

 countries), we seldom have ice-bound marine coasts. 

 And hence animals of salt waters, which are in many 

 points different to those of fresh water, and more liable 

 from their structure and sedentary habit to be injured 

 mechanically by such ice, as well as by its cold, are not 

 so harmed, by reason of these wise modifications of laws. 

 And even when sea water does freeze, its ice is not 

 salt, but fresh, and thus, by its specific gravity being 

 much less than that of the water in which it floats, 

 it stands comparatively higher out of that fluid than 

 if the latter were fresh water, and thus winds un- 

 doubtedly get a greater hold on it, and its dispersion 

 is the speedier. And if sea water froze as readily as 

 fresh water does, so that our islands of Britain were sur- 

 rounded periodically by masses of ice, their presence 

 generally, and the increased coldness of the winds blow- 

 ing over them, would materially change our climate. 

 How amazingly wonderful is all this interdependence 

 of cause on cause, and law on law, no matter how 

 small or trifling they may appear to our dull wits : — 



" And if each system in gradation roll, 

 Alike essential to the amazing whole, 

 The least confusion, but in one, not all, 

 That system only, but the whole must fall."* 



Lower Norwood. 



* The above four lines I lately read in the Times newspaper 

 for 1831. No author's name is given, but I should be glad to 

 know it. 



ORNITHOLOGICAL ESSAYS. 



No. III. — THE Sparrowhawk [concluded). 



By Tom Wm, Dealy. 



NEXT to the kestrel (Falco tinnuncnlus) the spar- 

 rowhawk is the commonest of the birds of prey 

 which inhabit the British Isles. Its favourite resorts 

 are among the wooded districts of mountainous regions, 

 or in extensive demesnes, also in various situations, 

 where, amid the savage repose of nature, it can bring 

 up its young in undisturbed tranquillity ; yet where it 

 is within easy access of places whence it can command 

 a sufficient supply of sustenance. Though this hawk 

 nestles in woods, it beats about in more open situations, 



Fig. 196. — The Merlin (Falco ccsalon). 



such as along the borders of some well tended preserve. 

 See how stealthily, watch how warily, it flies in sub- 

 dued speed up the hedgerow, and down the side of 

 yonder plantation, on the alert for its morning meal. 



In Scotland, according to Macgillivray, both the 

 merlin [Falco asalon) and the kestrel are familiarly 

 known by the name of sparrowhawk. Like all 

 others of the Falconidae, it has to flee before the 

 unrelenting hand of agriculture. Some murmur at 

 this, and would fain see birds adapt themselves to 

 the alterations of the land's surface. And yet, how 

 incongruous it would appear to behold the golden 

 eagle [Aquila chrysaetos), in all its slow majesty of 

 wing over our meadow lands. Much as we regret 



