456 



ON THE DETERMINATION OF THE TEUE STRENGTH 



5. Fresh breeze, . . 



6. Strong breeze, 



7. Moderate gale. 



8. Fresh gale, 



9. Strong gale, .. 



10. Wliole gale, .. 



Or that towhichshe could just carry 

 in chase, full and by . 



11. 

 12. 



Storm, 



Royals, &c. 



Single-reefed topsails and top-gallant-sails. 



Double-reefed topsails, jib, &c. 



Triple-reefed topsails, &c. 



Close-reefed topsails and courses. 

 Or that in which she could scarcely bear close-reefed main-top-sail and reefed 



foresail. 

 Or that which would reduce her to storm-staysails. 



Hurricane, Or that which no canvass could withstand. 



But although this was at the time a gi-eat improvement on the old system, 

 it is by no means sufficient for the requirements of the present day ; for so much 

 is still left to the feelings and experience of each observer, that one officer will say 

 that the wind should be marked as No. 4 ; while his companion may say it is 

 rather No. 5, and another may decide on 3 being the more appropriate expressive 

 number. 



But even supposing that they were all agreed on this point, and said the wind 

 was 4 in strength, no one has ever attempted to determine what that number, or 

 any other in the table, really means, — what natural strength of the wind, or what 

 velocity of the air, it is equal to. A simple inspection of the table shews that the 

 scale is by no means a uniform one ; for, between Nos. 1 and 2, there can hardly 

 be a difference of ift pressure of the wind on the square foot ; while between 11 

 and 12, there may be 20 or 30t) difference. 



Now, this is an imperfection in the system of the gravest kind, for if the strength 

 of the apparent wind be not observed in such terms as are reducible to those in 

 which the velocity of the ship is measured, the strength of the true wind, or that 

 which a person would feel if perfectly at rest on the ocean, cannot be determined ; 

 and the real motions of the atmosphere would be concealed to a great and un- 

 known extent, by the effects of the movement of the ship. 



These defects are of consequence, too, even in ordinary practical matters, as 

 in trial squadrons ; for it is not the 'il>.<,>bila speed of a ship which is wanted, but 

 the relative speed of it, with regard to the wind ; and the winds, blowing at the 

 same time on the various ships several miles asunder, may be of very different 

 strengths ; as any one may prove to himself, by noting the capricious streaks, in 

 which, after a calm, a change sets in on the surface of the water. It is true, that, 

 by keeping the ships out a long time, a mean may be obtained of all these little 

 atmospherical currents, but the result will not be satisfactory ; and, as in the cele- 

 brated case of the three trial brigs, there may be a total difference of opinion on 

 the absolute merits of each vessel, by reason of the cause of the apparent su- 

 periority, now of one, and now of another, not being properly understood. 



These difficulties are all of the character which would be removed by an instru- 

 mental method of determining the strength of the wind ; and this is not the first 

 time that the use of an anemometer has been proposed on boardship ; but those 

 which have hitherto been tried would seem to have failed, from not having been 

 of the appropriate kinds ; and partly, indeed, because, in the case of those officers 



