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THE POPULAR SCIENCE MONTHLY. 



particular case. The author has found that, 

 in general, they are of no practical assist- 

 ance to the student, and even in some cases 

 [are] confusing." 



How an interpolation is to be made un- 

 less by the aid of a formula, the author does 

 not tell us, although the mind naturally is 

 anxious upon so important a point. 



He goes on to add a practical precept, 

 however, to the effect that he desires to 

 impress upon the student the importance 

 of obtaining the Greenwich time " almost 

 invariably" before consulting the "Alma- 

 nac." As the " Nautical Almanac " is so 

 constructed that no element can be taken 

 from it without a knowledge of the Green- 

 wich time, it seems almost a work of su- 

 pererogation to " impress " this fact at the 

 26th page of a work on navigation. 



But, allowing these two practical pre- 

 cepts to stand as examples of the conclu- 

 sions which the author's experience at sea 

 has led him to, let us briefly notice some 

 of the more important features of the early 

 portions of the treatise, remarking that, to 

 fulfil its purpose as a suitable text-book, 

 these should be exact and clear ; and, fur- 

 ther, remembering that it is important that 

 the interests of the student should be sedu- 

 lously guarded, and that his first ideas 

 should be of the most definite nature and 

 strictly correct. 



Let us remember, too, that a very poor 

 book, of no peculiar importance in itself, 

 has a claim to notice in an educational 

 point of view. There is hardly a middle 

 ground between goodness and badness in 

 such a one : if it be good, let us have it 

 by all means ; if bad, it is a duty to warn 

 others against it. 



Perhaps there is nothing more impor- 

 tant to the navigator than a clear concep- 

 tion of the astronomical ideas of time, lati- 

 tude, and longitude. " Longitude," says 

 our author, " is the angular distance be- 

 tween any meridian and a fixed or prime 

 meridian. It may be considered as an 

 angle at the pole," etc. 



Longitude of what ? Any definition of 

 longitude should begin, " the longitude of 

 a place is," etc. There is no abstract thing 

 called longitude ; but there is a certain 

 definite coordinate for every point on the 

 earth's surface, which is the object of the 



definition. The same objection applies to 

 the definition of latitude. 



On page 18 we learn that " time is the 

 hour-angle of some heavenly body, whose 

 apparent diurnal motion i3 taken as a meas- 

 ure." Now, there is such a thing as time 

 in the abstract, portions of which we meas- 

 ure, or have measured for us, by certain 

 recurring phenomena. 



The explanations of apparent time and 

 of the equation of time are equally faulty ; 

 but imagine the surprise of the astronomer, 

 who is told that " astronomical time com- 

 mences at noon, and is measured toward the 

 westward 1 ' " 



From this, to measuring eternity toward 

 the northeast, is but a step. It is evident 

 that, in the author's mind, the words " time " 

 and " day " were equivalent. 



With these fundamental errors in the 

 book, it is scarcely probable that it should 

 not be faulty in other ways. And, indeed, 

 it will be found in many points inaccurate, 

 confused, often unintelligible. Perhaps it is 

 hardly necessary to mention certain other 

 faults of the book, which are still discred- 

 itable. Many of its demonstrations arc 

 taken directly from other text-books, and 

 in no instance, we believe, is a proper ac- 

 knowledgment made. Its chapter on the 

 Compass is reprinted, almost verbatim, from 

 a pamphlet published by the Navy Depart- 

 ment on the same subject, and, although 

 the author probably meant to do no injus- 

 tice, no mention is made of this fact in any 

 way. 



On the whole, we must set this down as 

 a harmful book, being full of doubtful state- 

 ments, of confused mathematics and ques- 

 tionable precepts, and one not likely to im- 

 prove the art of navigation, or the science 

 of nautical astronomy, in any way. 



The Coal-Regions of America : their To- 

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 By James Macfaulane, A. M. 8vo, 679 

 pages. New York : D. Appletou & Co. 



Those who understand how closely our 

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 comprehensive and fully-illustrated work 



