C 365 ] 
difiindt and free from any corona, or circle of aber- 
ration, and the fun’s limb perfectly well defined. 
For my own part, he appeared to me, thro' a reflec- 
tor of four feet focus, magnifying about 1 3 y times, 
as truly defined as I could wifh to fee a black cir- 
cle upon a white ground. 
I muff, however, upon this occafion, take notice, 
that, during the whole time of this* tranfit of Mer- 
cury, the air was perfectly calm with us j but that, 
in the two laft tranfits of Mercury over the fun, 'viz. 
in the years 1736 and 1743, both the fun’s and Mer- 
cury's limbs appeared to me indift inct, aud furrounded 
with fomething like what this gentleman calls a lu- 
minous crown, or circle of aberration ; tho’ I, at 
both thefe times, made ufe of reflecting telefcopes, 
which I had, by former trials, efteemed good. But 
it is to be obferved, that, during both thefe tranfits, 
there was a conftant hard gale of wind ; and as I had, by 
other obfervations, formerly found, that the images 
of the planets, in the night-time, did not appear fo 
diftinct in windy weather, as when it was calm, I 
therefore imputed the indiftinctnefs of the fun’s and 
Mercury’s limbs to the air’s being agitated by the 
wind *. And of this we may be made fenfible by 
a familiar in fiance : 
Suppofe a vefiel full of water, having any thing 
lying at the bottom, fuch as a fhiliing, the water being 
at refi ; you will then perceive the image of the {hil- 
ling difiinctly ; but if you give any commotion to the 
water, the image of the fhiliing will then appear in- 
difiinct and confufed. 
* Since this paper was read, Mr. Short has been informed by M. Le 
Monnier, the French King’s aftronoiner, that, during the laft tranfit at 
Paris, they had a hard gale of wind from the N . E. 
Somewhat 
