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THE POPULAR SCIENCE MONTHLY. 



upon the surface of the bergs was of daz- 

 zling whiteness, but, in places, faint discol- 

 orations, due not to earthy matter, but to 

 the presence of birds, were observed. . Prof. 

 Thomson concludes that the ice from which 

 the bergs were broken was found upon low, 

 level land that was surrounded by shallow 

 water. 



Although no debris were seen upon the 

 bergs, it is quite certain that large quantities 

 of them were held in their under portions, 

 whence they dropped into the sea, as such 

 deposits were continually brought up by 

 the dredge. 



Prof. Thomson suggests that the in- 

 crease of glaciers in thickness may be lim- 

 ited by melting at their under surface from 

 pressure of the mass. A column of ice, 

 1,400 feet high, he estimates to lie upon the 

 ground with a pressure of nearly a quarter 

 of a ton to each square inch of surface, nor 

 does he find reason to doubt that the tem- 

 perature of the earth's surface beneath the 

 glacier is about 32. He cites the fact that 

 from beneath glaciers in Greenland muddy 

 streams are continually discharged. It is 

 possible, therefore, that the antarctic gla- 

 ciers, covering vast level tracts, are pre- 

 vented from accumulating to a thickness 

 much exceeding 1,400 feet, by waste in the 

 bottom portions, where constant melting 

 and regelation are going on. 



On the chart of the American explorer, 

 Lieutenant Wilkes, a position is given for 

 what he called Termination Land. On close- 

 ly approaching the spot, no land was found, 

 and Prof. Thomson was " forced to the con- 

 clusion that Lieutenant Wilkes was in error." 



The interesting fact was revealed by 

 soundings that a layer of water 300 fathoms 

 below the surface was warmer by several 

 degrees than water at the surface, and it 

 was ascertained that the heat increased 

 northward. Hence it was concluded that 

 the source of the warm water was north- 

 ward, and that it may have been deflected 

 by the southward projection of continental 

 lands, turning southward currents which 

 have their origin in the " great drift-cur- 

 rent which sweeps round the globe." 



Animals and Steam-Engiues. A writer 

 in Dinglev^s Polytechnisches Journal, in not- 

 ing the behavior of different animals tow- 



ard the steam-engine, remarks upon the 

 dexterity with which dogs run about among 

 the wheels of a departing railway-train with- 

 out suffering the least injury, whereas a 

 host of railway workmen annually lose their 

 lives. On the other hand, the ox, a pro- 

 verbially stupid animal, continues standing 

 composedly on the rails, having no idea of 

 the danger which threatens him, and is run 

 over. Many kinds of birds seem to have a 

 peculiar delight in the steam-engine. It 

 has often happened that larks have built 

 their nests and reared their young under 

 the switches of a much -traveled railway. 

 In engine-houses the swallow is a frequent 

 guest. In a certain mill, where a noisy, 

 three hundred horse-power engine works 

 night and day, two pairs of swallows have 

 built their nests for years, and rear their 

 young there regularly. A case of almost 

 incredible trustfulness on the part of swal- 

 lows occurred in the early part of last year, 

 when a pair of these birds built in the pad- 

 dle-box of a steamer, and regularly made 

 the journeys from Pesth to Semlin. The 

 author concludes with this caustic remark : 

 " I have never yet found any animal at home 

 in the boiler-house. Even the dog steers 

 clear of boilers. It is almost as if the low- 

 er animals knew what an amount of stu- 

 pidity and folly appears in our construction 

 of boilers." 



Prof. Dana on Cephalization. The fifth 

 of Prof. Dana's interesting papers on" Ceph- 

 alization " is published in the American 

 Journal of Science and Arts for October. 

 The author's thesis here is that cephalization 

 is a fundamental principle in the develop- 

 ment of the system of animal life. As the 

 animal grade rises, there is a compacting of 

 structure in both the fore and hinder parts 

 of the body. Of mammals the lowest forms 

 are those having their locomotive functions 

 in the posterior parts of the body, while in 

 the higher forms the forces or force-organs 

 are more and more forward in the structure. 

 There are large size and strength behind in 

 low forms, but a compacting of these and a 

 better head in the higher. 



The head becomes more and more the 

 centre of nervous energy or force as devel- 

 opment goes on, and this is to be seen in 

 the specific forms of Nature. "Here form," 



