VOL. LXVII.] 



PHILOSOPHICAL TRANSACTIONS. 



199 



posed to have happened sometimes between the times of observation, though at 

 these times the wind might have been below the mean ; to compensate this 

 defect, hurricanes are included in the computation. From the table then we 

 have the following proportions of the '2 degrees of winds and upwards, to those 

 below ; and also of the mean between those 2 degrees. 



Dayb. 



Winds of the 2d degree and upwards in each week 4.283 



Cahns and winds below the 2d degree 2.7 1 7 



Winds of the 3d degree and upwards O.902 



Cahns and winds below the 3d degree 6.098 



Winds of a mean proportion between the 2 preceding degrees . . 2.592 

 Calms and winds below the mean degree , . 4.408 



From this computation we have l.bQI days 

 in a week, or 1 9-307 weeks in a year, in which 

 wind machines of the heavier kinds, and of 

 considerable friction, may be supposed to be 

 kept in motion ; which, to the times in which 

 they cannot go, is as 10 to 17- It may be ob- 

 served, that the resistance to the machine, or 

 its weight and friction, being diminished, though 

 in a small degree, will add considerably to the 

 frequency and length of times in which it can 

 go ; since it often happens that there are winds 

 immediately below the lowest degree in the pre- 

 ceding estimate, sufficient to keep the lighter 

 machines in motion. Hence those who have 

 machines which are not absolutely of the hea- 

 viest kind, will be apt to conclude this computa- 

 tion erroneous. Besides, there are few who 

 make allowance for, or attend to the universal 

 law which obtains in mechanics, that in larger 

 machines, their power doth not increase in a 

 proportion so high as their bulk and the resist- 

 ance arising from their friction. The table, for 

 each month, on an average of 5 years, is an- 

 nexed. 



A Table, showing the Proportion of 

 IVinds of the id degree and upwards, to 

 those of the 1st and below ; also of the 3d 

 degree and upwards, to those of the 2d 

 and below ; for each month on a medium 

 of 5 years. 



XXVII. Description of the Jesuits Bark Tree of Jamaica and the Caribbees. 

 By IVm. IVright, M.D., Member of the Philos. Society of America, and 

 Surgeon-General in Jamaica, p. 504. 



This species of Jesuits bark grows on stony lands near the sea-shore, in the 



