Manchester Memoirs, Vol. xlv. (1901), iV^. 11. 3 



but LiM = LgP, therefore 



LiN.LiF = L2P.L2H. 



Q.E.D. 



The above is the geometrical construction, giving a 

 projection which has been long known in its analytical 

 aspect. Professor Lamb has pointed out to me that the 

 analytical solution is to be found in Craig's " Treatise on 

 Projections," p. 112. The particular case when the vertical 

 angle of the cone is a right angle has been called by 

 Germain, " Lambert's isospherical stenoteric projection." 



