ipo 



THE POPULAR SCIENCE MONTHLY. 



correspond with the first force in the 4th cohimn, the second sum of 

 hours with the second force, and so on. 



As the direction of the wind is given on the charts for only the 

 alternate points, the observations of the intermediate points are dis- 

 tributed among those adjacent. Suppose the transfer of the observa- 

 tions of the sheets of Form B, for one point, to stand on Form D 

 thus : 80 + 120 -|- 300 + etc. . . . (hours) . . . . N. by W. . . . 

 5 ; 3 ; 2 ; etc. . . . (Force). The point N. by W. not being used, 

 all these observations must be distributed between !N'orth and North- 

 northwest — half to each : i. e., 40 hours, force 5 ; 60 hours, force 3 ; 

 and 150 hours, force 2, must all be placed opposite North, and the 

 same opposite N. N. W., just as if they had come from the sheets of 

 Form B. The " Total No. of hours of wind from every alternate 

 point " is now found by adding up the separate periods, and the sum 

 is placed in the 1st column opposite its own point. To obtain the 

 mean force for this sum, each separate period of hours is multiplied 

 by the force peculiar to it, the products are added together, and their 

 sura is divided by the " Total No. of hours of wind from every alter- 

 nate point " ; the quotient is the " Final mean force," which is accord- 

 ingly placed in the 5th column. The totals of " Calms " and of 

 " Variable winds " are now found, and carried out to the 1st column ; 

 then all the figures in this column are added up, and the result is the 

 " Total No. of hours of wmds, calms, and variables " observed in 

 square No, 643 during the month of July. To complete the treat- 

 ment of the winds, the percentage that the total number of hours 

 from every alternate point, as well as the percentage that the calms 

 and the variables are of the total number of hours of observation in 

 the square, are worked out and entered in the 6th column. 



On the back of Form D are columns for collecting the other data 

 scattered over the sheets of Form B, viz. : 1, Barometer and thermom- 

 eters. Beside the mean of each of these quantities transcribed from 

 Form B is placed the number of hours of observation from which that 

 mean is deduced, so that, in obtaining Wq filial mean of the square for 

 the month, due weight can be given to each individual mean. 2. The 

 separate mean daily ranges of the preceding items, with the number of 

 days of which the mean is formed written beside it ; 3. The regular 

 daily oscillations of the barometer ; 4. The highest and the lowest 

 readings of the barometer and dry-bulb, with the period during which 

 each separate observation was made ; 5. The total number of hours of 

 fog, of rain, of squalls (heavy and light), and of gales from each quar- 

 ter, with their strength ; and, 6. A summary of the currents, weather, 

 and magnetic variations. To complete Form D, a resume of the re- 

 marks on the various sheets of Form B is made — a generalization of 

 the experiences of the several ships — and transcribed to the back of 

 the form. When the observations of every square for each month are 

 collected on sheets of Form D in the manner described, the reduction 



