1819.] and the Upright Growth of Vegetables. 33 



mandate, by reason of the rapid revolution of the wheel. Gravi- 

 tation, therefore, could have no sensible effect on the vertical 

 wheel ; but it would appear, that when the horizontal wheel made 

 80 revolutions per minute, the centrifugal force was just equal to 

 gravity. 



Indeed if the length of the radicle bore any considerable pro- 

 portion to the radius of the horizontal wheel, it ought to have 

 been a little curved, or more horizontal, toward the extremity ; 

 but the reverse would take place with the direction of the germen. 

 Had great attention been paid to the direction of the growth, it 

 would probably have been found a little pointed backward from 

 the radius in both wheels, in consequence of the resistance of 

 the air. 



I have often observed in the growth of wood, that when a tree 

 did not stand upright but leaned tu a side, the annual growths 

 or tubular coatings were much thicker on the under than upper 

 side. In branches shooting out horizontally, the difference was 

 still more remarkable ; but this is sometimes counteracted by 

 another circumstance — that when trees are very crooked, the 

 hollow side of a turn fills up, or grows much more rapidly than 

 the round side ; so that the juices seem disposed to take the 

 shortest road. This appears to be the reason why some sorts of 

 trees, though extremely crooked when young, gradually straighten 

 as they advance in years. I am, Sir, 



Your most obedient servant, 



Henry Meikle. 



P. S. — There is still something inaccurate about the mean 

 degree of latitude deduced from Col. Lambton's measurements, 

 contained in your number for March. From the table there 

 given, it appears to me that the degree at the latitude of 45° 

 (usually taken as the mean) is 69 - 0361 miles, or t>9-~- nearly, 

 which is still further from 69^-, than the former number. H. M. 



* # * The length of a degree of latitude at 45° given by Col. 

 Lambton is 60751-K fathoms = 69-036 miles (the number 69-030 

 is by an error of the press for 69*036). When I said that the 

 mean length of a degree of latitude was nearly 69— miles, I 

 meant for Great Britain, and particularly for London.— T. 



Vol. XIV. N° I. 



