158 



Specimens of the subjects of this paper were exhibited by the 

 author, and may be seen in the Society's museum. (See Plate.) 



3. On Aplanatic Telescopes, a posthumous paper by the late 

 Archibald Blair, Esq. Communicated by Professor 

 Forbes. 



In this paper a new fluid composition is proposed for correcting 

 chromatic aberration, free from the corrosive properties of those 

 tised by the author's father Dr Blair, the inventor of the fluid ob- 

 ject-glass. The composition proposed is : — 



Saturated solution muriate of lime, ' . . 40 parts 



< nitrate of lime, . . 20 ... 



Strongest acetic acid, 2 ... 



The secondary spectrum formed by the nitrate, combined with 

 crown-glass, is similar to that when flint and crown glass are com- 

 bined. The combination of crown-glass with the muriate is the 

 opposite. Hence, by properly combining these, Mr Blair states 

 that the secondary spectrimi may be wholly destroyed. 



Monday, \fith January 1837. 

 Sir THOMAS M. BRISBANE, President, in the Chair. 



The following gentlemen were duly elected Ordinary Fellows 

 of the Society : 



1. John S. Russell, Esq., Lecturer on Natural Philosophy. 



2. Charles Maclaren, Esq. 



3. Archibald Smith, Esq., Fellow of Trinity College, Cam- 



bridge. 

 The following Donations were presented : 

 Comptes Rendus Hebdomadaires des Seances de I'Academie des 



Sciences de France, (2d Semestre 1836), Nos. 25, 26.—% 



the Academy. 

 On the Unity of Structure in the Animal Kingdom. By Martin 



Barry, M.D., F.R.S.E.— .By the Author. 

 Transactions of the Institution of Civil Engineers. V^ol. i — By 



the Institution. 

 Nouveaux Memoires de la Societe Imperiale des Naturalistes de 



Moscow. Tome iv. 

 Bulletin de la Societe Imperiale des Naturalistes des Moscow. 



Tome ix. 



By the Imperial Society. 



