1Q8 PHILOSOPHICAL TRANSACTIONS. [aNNO 1777. 



represent to you all particulars; and it is hoped you will comply therewith. In 

 this country, worship of the Almighty is the profession of all. We poor 

 creatures are in nothing equal to you; having however a few things in hand, 

 I send them to you by way of remembrance, and hope for your acceptance of 

 them." 



XXf^I. Of the D'igrees and Quantities of [Finds requisite to Move the Heavier 

 kinds of Wind Machines. By John Stedman, M. D. p. 493. 

 The irregularity and uncertainty of winds in this country have been found a 

 considerable discouragement to erect wind machines. These machines are sel- 

 dom erected with us, unless where a considerable moving power is necessary. 

 This is always the case where the larger kind of pump-work, is to be kept in mo- 

 tion, or where water is to be extracted from deep pits. Having inquired of many . 

 people concerned in such works, what may be the proportion of time in which 

 wmd machines may be kept in motion, to that in which they cannot move from 

 a defect of wind, it is found tliat these people ditier widely in their conjectures. 

 The only method of bringing the matter to a proper estimate is, by comparing 

 the quantities of winds sufficient for moving these machines, with those of winds 

 below that degree, and calms. This computation can only be drawn from jour- 

 nals in which the degrees of winds are noted. In the meteorological register of 

 the Medical Essays of the Edinburgh Society, there is a column of winds, and 

 4 degrees are noted. This division is sufficient for the purposes for which that 

 register was intended ; but when we consider the wind as a power acting on ma- 

 chines, that number of degrees will be found too small. Thus, from the 2d in 

 that register to a hurricane, there is but 1 intermediate degree. As the 'id de- 

 gree, which is very moderate, is insufficient for moving these machines ; the 

 3d is more than just enough for that purpose. A degree therefore which is a 

 mean between these 2, will be found to be the lowest that is sufficient for 

 moving machines of the heavier kinds, particularly such as are used for pumping 

 water out of coal-pits. These 3 degrees of wind, that is the 2d and 3d of the 

 Edinburgh register, and an intermediate degree, are very distinguishable even by 

 the senses, and without the assistance of any instrument, by those who are at- 

 tentive, and have been accustomed to make observations of this nature. 



To ascertain proportions of this nature, a longer te/m of years would have 

 been more satisfactory ; but in case others should afterwards pursue this kind of 

 computation, the proportions are digested in a table at the end of this essay, and 

 may be consulted occasionally. In making up this table, viz. of the 2d degree 

 and above, and of the 3d and upwards, hurricanes are included, though that 

 degree of wind be too high for any machine. But as the observations were taken 

 twice in 24 hours, and as winds sufficient to move these machines may be sup- 



