52 



lowing are the results— the numbers in column (2) being the 

 quotients got by dividing those in column (1) by the respec- 

 tive atomic weights : 



(1) (2) (3) 

 Sulphuric Acid, . . . 32.79 .817 4.000 



Alumina, 10.65 .414 2.026 



Oxide of Manganese, . 7.33 .205 1.003 



Sulphate of Magnesia, . 1.08 



Water of Crystallization, 48.15 5.350 26.315 



100 



The numbers in column (3) being almost exactly the in- 

 tegers, 4, 2, 1, and 26, show that the substance analyzed is a 

 true alumn, having, as respects its acid and bases, the same 

 formula 



(3so 3 , a/ 2 o 3 + so 3 , mwo + 26ho) 

 with all the known species of that genus, and the same 

 number of atoms of water with soda alumn. It differs from 

 all those previously known in containing no alkali, this being 

 replaced by protoxide of manganese. As an additional pe- 

 culiarity Dr. A. observed that it did not appear susceptible 

 of assuming the octohedral form. 



The paper concluded with some remarks upon the pro- 

 bable existence of an alumn containing no metal but manga- 

 nese, and upon certain difficulties in the doctrines of isomor- 

 phism, suggested by some of the varieties of this class of salts. 



Captain Portlock brought under the notice of the Aca- 

 demy some peculiar habits of the Otus Brachyotos, or short- 

 eared owl, lately observed by Captain Neely, whilst collect- 

 ing for the Ordnance Survey of Ireland. 



This species of the sub-genus otus being migratory, is 

 much rarer than the otus vulgaris, or long-eared owl, and it 

 differs from it in many striking respects, such as the small 

 size of the elongated feathers, commonly called ears, which 



