1 i<9 ] 
On Examination, I find the five Appearances to 
anfwer the five Stamina on which the Apices are fet ; 
and from this Appearance, growing nearer and nearer 
to each other by degrees, they join at laft all in one 
in the Stalk of the Flower. 
' t ' r - ' ' 1 5 O I’/' : I f . I l ;I; r •;> i 
— — — — — ■ ™ — — « 
XIII. Part of a Letter from Mr. Wra, Arde- 
ron, F. R. S. to Mr. Henry Baker, F. R. S. 
concerning an Improvement of the Weather- 
Cord. 
SIR, 
Read April z\. r ■ "’HE Weather Cord is an Hygrometer 
174 ' of a very ancient Invention, and* 
if properly conttru&ed, may be made ufe of with very 
good Succefs, to (hew the various Alterations of the 
Atmofphere, in refpeft to Moifture and Drynefs ; but, 
as commonly made, it never rifes or falls lufficiently 
to point out fuch minute Changes as the Curious 
would be defirous to know. A Senfe of this Defeat fet 
me upon endeavouring to find out fome Method of 
removing it ; and how far I have fucceeded, will beft 
appear upon calling your Eye upon the Drawings, 
Tab. II. Fig. 4. and Fig. 5. 
In the firft of thefe Hygrometers which I made, as 
in Fig. 1. I only fixed the End of the Index A B fall 
to the Silk CE at A, leaving it lying loofe upon 
the Point D ; and in this manner the other End of 
the Index would nearly defcribe the Arch FGH : 
But then I foon perceived, that the Centre of Motion, 
Y a whereon 
