NOVEMBEE 27, 1908] 



SCIENCE 



767 



development of the chart from the earliest 

 known map to the present time, indicates the 

 purpose and character of the one million 

 nautical charts now published each year, and 

 shows the present state of advancement of 

 surveys for charting purposes. A double page 

 reproduction of the earliest extant chart show- 

 ing America is to be found in this chapter. 



The collection of information for charts is 

 treated in 34 pages. An excellent statement, 

 fully illustrated by photographs and drawings, 

 is made of the methods of surveying employed. 

 The essential difficulty of making certain, even 

 in a closely surveyed region, that no isolated 

 pinnacle rock reaches up so near to the sur- 

 face as to be a danger to navigation, is clearly 

 indicated by text and illustration. An 

 example is given of the recent discovery, in 

 Blue Hill Bay, Maine, by the use of a wire 

 drag, a special device for that purpose, of a 

 pinnacle rock only six feet in diameter at its 

 top. The rock has but seven feet of water 

 upon it, although it is surrounded by depths 

 of 78 feet, from which it rises nearly perpen- 

 dicularly. The caution necessary in sifting 

 evidence in regard to reported dangers to 

 navigation and in making examinations for 

 such reported dangers is illustrated by nimier- 

 ous concrete examples. It is important that 

 chart users should have some knowledge of 

 these matters in order that they may know 

 what reliance they should place upon charts, 

 upon the one hand, and what reliance to place 

 upon hasty criticisms of charts, upon the 

 other hand. 



In the chapter of 19 pages, entitled. Prepa- 

 ration of Information for Charts, descriptions 

 are given of the mercator projection, the 

 polyconic projection and the gnomonic pro- 

 jection, and the special advantages of each are 

 stated. The necessary limitations of each are 

 also indicated. These are the three pro- 

 jections which one must understand to use 

 charts intelligently. 



Thirteen pages on the Publication of Charts 

 are devoted mainly to a short enumeration of 

 the various processes involved in passing from 

 the drawings to the printed charts, such as 

 engraving on copper, copperplate printing, 

 printing from stone, photolithography, etch- 



ing, etc., and of the advantages and disad- 

 vantages of each process or combination of 

 processes now in use. 



The imperative need for frequent correction 

 of charts is treated in 15 pages. The average 

 loaded draft of the twenty largest steamships 

 was 24 feet in 1872 and 32 feet in 1903. 

 Channels and harbors are dredged and other- 

 wise improved and changed. Great natural 

 changes take place. An island of sand has 

 moved northwesterly for two miles directly 

 across the mouth of the Columbia River in 

 Oregon during the years 1851-1905 and has 

 closed up the former channel. An average of 

 400 new rocks and shoals, dangerous to navi- 

 gation and not previously shown on charts, 

 are reported each year, according to British 

 reports. Of the 367 reported in 1906 only 11 

 were discovered by vessels striking them. 



In the last three chapters of the book (48 

 pages) there is brought together in convenient 

 form for reference much information of value 

 to the navigator who has the charts before 

 him and desires to understand and use them. 

 He wiU there find the charts explained; will 

 find clear general directions given for plotting 

 upon the charts, for locating a vessel from the 

 results of astronomic observations, as well as 

 by dead reckoning, by compass bearings, by 

 sextant angles, and by sounding; and will find 

 certain precautions which are advisable in the 

 use of charts stated with the reasons for them. 

 The book closes with six pages in regard to 

 the various publications in book and chart 

 form which are necessary or convenient for 

 use in connection with nautical charts. 



For any one having to do with charts, this 

 book contains much useful information, set 

 forth in the form of a handbook rather than of 

 a technical treatise. For mariners, yachts- 

 men, surveyors and shippers it is of special 

 interest. The expert in the lines treated wiU 

 find it valuable in furnishing a good general 

 view of the subject by an expert. The book 

 is up to date, is written in an interesting 

 manner, and yet is especially to be commended 

 for laying emphasis upon matters which are 

 really important to the users of charts, rather 

 than the matters which are merely interesting. 



J. P. H. 



