194 THE POPULAR SCIENCE MONTHLY. 



they do not form the basis of the charts. That basis is the variety of 

 observations comi^iled and reduced in the careful and laborious manner 

 already described, and which have then been examined from every 

 standpoint to elicit whatever beam of information they might contain 

 to illumine the ocean highways. Therefore, in justice to the amount 

 of thought, care, and labor bestowed on these charts, it must be stated 

 that they are not a rearrangement of old matter, but are essentially 

 new, and from original sources. 



The second series of charts (now in course of compilation) embraces 

 a series for the whole Atlantic between the parallels of 60° north and 

 60° south. The observations of the direction of the wind on Maury's 

 pilot-charts, to the number of about 2,600,000, or 300 years, will be 

 embodied in them : the actual period over which these observations 

 extend is from the year 1800 to 1855. But, as with the Pacific charts, 

 the real groundwork of the Atlantic series is the various kinds of ob- 

 servations at present compiled in the careful manner already described 

 from recent log-books and meteorological journals. In number, these 

 observations will amount to about 650,000 hours, or 75 years. The 

 actual period over which they will extend is from the year 1855 to 

 1881, the time when it is confidently hoped this set will be ready for 

 issue. By far the greater part of the compilation is already done. 

 The Atlantic charts, then, will contain hourly observations to the num- 

 ber of about 3,250,000, or nearly 375 years : in other words, if it were 

 imposed on a single ship to collect this mass of data, she would have 

 to cruise in all parts of the Atlantic during every month of the year, 

 for a period of 375 years, without ever going into port ! 



As, however, these observations were collected by a multitude of 

 vessels and during a continuous series of 81 years, several vessels were 

 observing at the same time in different jsarts of the ocean. Surely, 

 this is an abundance of facts that must render indisputable the in- 

 formation contained in the more frequented squares : more would be 

 mere accumulation, without perceptibly affecting the mean results. 



On some accounts it would be desirable to have the areas for which 

 the "information is classified smaller than 5° squares, as 1° squares, for 

 example ; but, again, there are objections, all but insuperable, to such 

 a system : 



1. To collect data for it suflicient to give trustworthy results, 

 would require a fleet of cruisers almost as large as the combined mer- 

 chant marine of the world — all to be assiduously engaged for many 

 years. This is unattainable. Even with the inducements now offered, 

 and notwithstanding that the undertaking is mainly for their benefit, 

 only a very small percentage of all the masters of merchant-vessels 

 will take the trouble to keep a meteorological journal with the requi- 

 site accuracy and care. Were it not for the excellent log-books of our 

 ships of war, our knowledge of the phenomena of the ocean would 

 indeed be most meager and inaccurate. 



