[ 1 84 ] 
Fig. 2 . the pofterior and under Side, which refted 
partly upon the Projlatte . This Side of the Stone 
was attach'd to the Bladder* 
a . the Place where the Body of the Bladder was 
contracted in Form of the Neck of a Gourd* 
b. the Extremity, which was lodged in the Be- 
ginning of the Urethra . 
c. the Impreffion made by the Nail of the Fore- 
finger of my left Hand, in palling it between the 
Stone and the Infide of the Bladder, in order to 
detach them from each other, and to dilate the 
Bladder fufficiently to introduce the Crochet. 
If. The Defcription of an Hygrometer made of 
a Deal Rod : Being Part of "Two Letters 
from Mr. William Arderon, FR.S. to Mr* 
Henry Baker, Fellow of the faid Society. 
SIR, * * * 
Read May 8. IT N OBober laft I contrived and made 
174 * JL an Hygrometer 5 thefirft Hint whereof 
I received from Obfervations on the Swelling of Deal 
Doors againft Rain. 
I perceived this Wood expanded itfelf very con- 
liderably, laterally, or acrofs its Grain : And this I 
imagined, if properly made ufe of, might fhew, not 
badly, the different Degrees of Moiflure or Drynefs 
in the Air. 
Thefe Thoughts fct me upon fearching the Philo- 
fophical Tranfaftions (as I do moft commonly, when 
I take 
