( ) 
to Dr, Halleys Account of it, in the Thilofophical 
Tranfa 6 lions (Numb. 183.) in which I entirely ac- 
quiefee, having always found it agreeable to the 
If by pubiifliing thefc Thoughts, I have explained 
the Rile of Vapours, in a more fatisfadory Way 
than has been done before ; or if I have only given 
nfeful Hints to others more capable of doing it, 1 
have my End. 
P. S. Since I have, for Brevity fake, only mentioned at what Heights 
from the Surface of the Earth, Vapours of different Denfities will come 
to an Jt'quiUbrium, without giving a Reafon for fettling the Place of 
JEquilibr'mn, atthofe Heights; I think proper to give the Method here 
by Avhich they are to be found, viz. As the Vapours will fettle and 
rife where the Air is of the fame Denfity with themfelves ; it is only 
required to find the Denfity of the Air at any Diftance from the Earth, 
at feveral Heights of the Barometer, which may be deduced from Dr. 
Ifalley's two Tables, Philofoph. Tranfaei. Niim. 386. (the Firft Ihewing 
the A.ltitude to given Heights of the Mercury, and the Second the 
Heights of the Mercury at given Altitudes ) and knowing the Degree 
of Heat by the Thermometer, becaufe the Denfity of the Vapour de- 
pends upon the Degree of Heat of the Seafon ; provided that proper 
Allowances be made for the great Rarefaftion of the Air near the 
Earth in hot and dry Weather, and the Condenfation of the Vapours 
in their Rife, by reafon of the Air being colder at a little Height above 
the Earth than juft at the Surface of it. 
IV. An Account offoyne Ohferyations relating to Na- 
tural Hiftory, made in a Journey to the Peak 
in Derbyfiiire, hy M*. J. Marcyn, F. ^ S, 
T H E Teak in T)erhyfhirey having hitherto been 
delcribed in fcarce any other Light, than as a 
Place compofed of Wonders; I was not a little de- 
ftrous to make Ibme Enquiry into the Nature of a 
Place generally efteemed one of the mod Surprizing 
of our own Country. 
’ In my Way thither, I took Notice of the follow- 
ing Plants, which I have not obferved to be com- 
mon 
