r *73 3 
tercepted fhort, there is the lefs chance of a change 
of refraction, during the time, between the middle 
and laft obfervation ; and therefore this method will 
be particularly ufeful in obfervations near the horizon.' 
Aullhorpe, April 17, 
1768. 
J. Smeaton. 
N. B. Obfervations of this kind may be made 
upon the planets in the day light, by 
making ufe of the. Sun for the firft obferva- 
tion, inftead of a flar; and waiting afterwards 
for the appearance of the ftars. 
XXVI. A 
