( 189 ) 
If the firft Incidence of the Ray be fuppofed to 
be in the Line E D, it will proceed in the fame 
Track as before, but with the contrary Directions; 
fo that the Angle E O B made between the firft in- 
cident Ray and the laft reflected, will till be equal 
ro the Double of G H N, as before. 
It is evident that on this Principle an Inftrument 
might be conftru&ed, the Effects of which would 
in a great Meafure refemble thofe of that before 
mentioned (N° 420 ) : But it would be liable to the 
Errors arifing both from the fpherical Figure of the 
Lens’s, and allb the different Refrangibility of the 
Rays of Light, when the Object is feen at a Di- 
ftance from the Axis of theTelefeope ; altho’ thofe 
Errors, by a- proper Difpofition of the Parts of the 
Inftrument, may be reduced to a very fmall Quan- 
tity. However, for this Reafon, and alfo becaufe 
the Inftrument feemed to me to be attended with 
greater Inconveniencies, both in its Conftruction 
and Ufe, than the other, I have not thought it ne- 
ceftary to give any more particular Defcription 
of it. 
V. Jn Account of a large Bony Suhftance 
found in the Womb, which was Jhewn to the 
Royal Society, May the 17th , 1753, by 
Edward Hody, M T>. F. ^ S. 
■£—« , aged 57, died in St. James's 
Market , January , 1725, In examining the 
! Pelvis of this Woman, I found a large Bony- 
B b " Sub- 
