244 
Gen . Roy’s Account of 
Feet, 
The height of the axis of the telefcope at Allington 
Knoll above low-water mark at fpring tides, as deter- 
mined by the obfervations there, and at the ftation of 
High Nook, is • • • • 3 2 9 
The axis on Tenterden Steeple has been (hewn to be 
lower than the Knoll . ®*7 
Therefore, the axis on Tenterden Steeple is higher 
than low water . 3 22 -3 
The arc of diftance of the two ftations «= io' 3". 3 being 
divided by i/ if'z the mean refraCtion, we have in this cafe 
or between \th and ^tb part for terrefrial refraSlion. 
The example in Art. IV. and this laft are given at large, 
becaufe, if the points where the axis of the telelcope was at the 
refpe&ive ftations had been obferved, in the firft, one would 
have been a depreflion, and the other an elevation ; but in this 
both would have been deprefled by obfervation. 
Art. VII. General Remarks. 
The three preceding examples being fufficient to (hew the 
mode that has been invariably adhered to in computing tne 
effect of terreftrial refraction, we have, in the following table, 
collected the whole of the refults together, beginning with 
thofe diftances where it has been found the greateft, and ending 
with thefe where it has been found the leaft. 
The titles at the tops of the columns refpeftively fully ex- 
plain the nature of the table, which contains more double ob- 
fervations, made on a greater variety of very accurate diftances, 
and with a better inftrument for determining fmall angles of 
elevation and depreflion, than perhaps were ever obtained be- 
fore. 
