196 THE POPULAR SCIENCE MONTHLY. 



ties in which it is eminently proper a sailor should be untrammeled. 

 No, a track-chart is a useful auxiliary — it partly solves the problem of 

 tracing the best course from port to port, and such a chart will eventu- 

 ally form part of the entire set ; but a full exhibition of all the data 

 on which the judgment is based is essential to every intelligent sea- 

 man. 



It is the log-books of ships of our own navy from 1855 to 1877 — 

 the large accumulation of twenty-two years — that are now undergoing 

 compilation at the Hydrographic Office for the series of charts de- 

 scribed : since 1877, by an order of the Navy Department, the compi- 

 lation is made by the navigator of each cruising ship. Being an offi- 

 cer of many years' experience at sea, and having direct and daily 

 supervision of the log-book, there is great advantage in having the 

 data ari-anged in the requisite form, on the spot and at the time of its 

 occurrence, by such a competent person. 



Both the observations and compilations are made with a definite 

 object in view, and, as that is to furnish charts for their future guid- 

 ance, it is an incentive to the officers engaged in their preparation to 

 make them as trustworthy as possible. The compilation is to con- 

 tinue until charts for all the frequented portions of every ocean are 

 published. 



When a log-book is full, both it and the compilations are sent to 

 Washington, where they are examined, compared, and used as found 

 necessary. 



In an article in a former number of this magazine, I have said that 

 it is impossible to predict, as is done on the land, what the weather 

 will be in various parts of the ocean for any short period ; there we 

 lack the stationary points of observation with direct and instant com- 

 munication : as pointed out by Maury, the most that can be done in 

 this way is to warn European countries by telegraph of the approach 

 of storms that traverse the Atlantic from the American Continent ; 

 and of late this has been successfully done by the " New York Her- 

 ald." 



In conclusion, I will merely allude to the utility of the charts 

 that form the subject of this article. If, on land, it be optional to 

 choose one's residence according to the salubrity of the climate, so at 

 sea, the mariner, with a panorama of the winds and weather spread 

 before him, can direct his course through only those squares that are 

 favorable and avoid the stormy. 



Moreover, the novice to the sea or the philosopher in his study can, 

 by a mere inspection of them, see what has passed over the waste of 

 waters during the last hundred years, and be more fully and accu- 

 rately informed regarding what in all probability he would have to 

 encounter, in the way of aerial phenomena in an ocean-voyage, than 

 the most weather-beaten tar that plows the main. 



