l68 PHILOSOPHICAL TRANSACTIONS. [aNNO 1738. 



nieated to the Society, containing 10 months of the year 1723, and Jan. 1724; 

 the author of which found by experiment, that in the place where his barometer 

 was kept, the Mercury stood y^ and -i^ higher than at the surface of the sea, 

 which was not far from his habitation. The mean height of the barometer for 

 those 10 months (leaving out the January following, which seems to be a very 

 irregular month) is 29.825, to which adding -jV 4-, it will give the mean height 

 at the surface of the sea 29.975 ; so the difference between these is only, 018, 

 and therefore probably may be near the truth, but may hereafter be more 

 exactly determined by experiments. Then allowing about 90 feet, or rather 

 less, for each 10th of an inch in height of the Mercury in smaller altitudes, or 

 in greater according to the tables calculated for that purpose, by Dr. Scheuch- 

 zer and Dr. Nettleton, and published in the Trans. N° 388, you will have the 

 height of each place pretty nearly, provided the observations be carefully made, 

 and continued for a sufficient time ; for the yearly mean heights, in one of the 

 places in these tables, appear to differ near -j^ of an inch in these two years ; 

 and in most of them, the last of these two years exceeds the first, two or 

 three hundredths: the barometer also ought not to be removed to a lower or 

 higher place. 



The thermometers agree, especially as to the hottest days in the year, more 

 than might be expected from places at such a distance. 



The winds are of so uncertain and variable a nature, that they require a 

 more than ordinary care and diligence in making the observations, and a 

 great length of time, and comparison of a vast number of them, before any 

 thing can be deduced more than is commonly known; and therefore he only 

 gives this hint, that if the observers would take particular notice, in great 

 storms, of the time when the Mercury first begins to rise, whether before, or 

 after, or in the very height of it, it might be a direction to judge when an 

 abatement or increase of it might be expected, if any regular order should be 

 found therein, which might be serviceable on some occasions. But if any 

 attempt should be made to lay down any thing certain concerning the rise and 

 progress of the variable winds, it will appear, by considering the cause of the 

 trade-winds, that for the same cause the motion of the air will not be naturally 

 in a great circle, for any great space, on the surface of the earth any-where, 

 unless in the equator itself, but in some other line; and, in general, all winds, 

 as they come nearer the equator, will become more and more easterly, and 

 as they recede from it, more and more westerly, unless some other causes 

 intervene. 



