Notices respecting New Books. 321 



On p. 15, and again on p. 21, we are informed that " a second 

 of space is about the sixtieth part of the smallest point distinctly 

 visible to the naked eye." This must depend on the eye and the 

 light ; we doubt whether, at a distance of 290 feet, any eye could 

 see a circle an inch in diameter as a circle ; but an ordinary eye 

 could see it in a good light at a considerably greater distance, and 

 Saturn with an apparent diameter of about 15" is distinctly visible 

 on a clear night. On p. 26 we read that " the force of rotation of 

 a globe like the earth, nearly 8000 miles in diameter, and spinning 

 round at the rate of more than 17 miles a minute, is quite sufficient 

 to render the position of its axis incapable of change." By position 

 we assume the author to mean position within the body of the 

 earth, because in space its position, or rather direction, undergoes 

 change from precession, in virtue of which it describes a cone round 

 a line at right angles to the plane of the ecliptic. The reason why 

 the line within the earth round which it rotates never varies much 

 from a mean position is neither the size of the globe nor its 

 angular velocity, but its shape. It is the bulge at the equator 

 which confines the axis of rotation to nearly one position within 

 the earth. On p. 45 we meet with the following statement : — 

 " The most remarkable instance of abnormal gravitation occurs at 

 the southern base of the Himalaya Mountains. In consequence 

 of it, we are told, the sea at Karachi, near the mouth of the Indus, 

 is 514 feet above the sea at Cape Comorin, the line of level being 

 raised to that extent by the attraction of the mountains." The 

 authority for this statement, we presume, is a paper by the late 

 Archdeacon Pratt, of which an abstract is given in vol. ix. pp. 597-9 

 of the Proceedings of the Royal Society. Subsequently, however, 

 the Archdeacon revised his calculation and brought out as a result 

 that, in consequence of the attraction of the Himalayas and the 

 deficiency of matter in the Southern Ocean, the sea would be 116 

 4-448 or 564 feet higher at Karachi than at Cape Comorin ; but 

 then he adds that, owing to counterbalancing causes, the change in the 

 sea-level is insensible (' Figure of the Earth,' 4th ed. pp. 233, 201). 

 On p. 73 our author expresses himself so incautiously as to lead 

 an uninformed reader to suppose that the image of a point seen by 

 reflection is formed on the reflecting surface. On p. 106 we come 

 on the following strange statement. Commenting on an opinion 

 of M. Pouillet, that the temperature of space is much above the 

 absolute zero, and that this is attributable to radiation from the 

 stars, our author observes, "He seems to have miscalculated 

 through forgetting that a high temperature can be brought about 

 only by a rise in the scale, and not by a multiplication of low tem- 

 peratures. If the heat communicated by each star be 32°, then the 

 heat of 10,000 stars will be no greater than that of so many 

 icebergs." 



On the whole Mr. Cooley has written an interesting and, in 

 some respects, valuable work ; but in the study of it the reader 

 will have to be on his guard, as the statements, though generally 

 trust worth v, are sometimes open to exception. Matters of specu- 



Phil. Mag. S. 5. Vol. 1. No. 4. April 1876. Z 



