PHYSIOLOGY AND NATUBAL HI3TOEY. 219 



crystal in which the new form occurs,) = 125° 5' ; making the vertical axia, 

 0,6082; whilst in the form iu question, the same angle is stated to be 149° 30' 

 which would give 0,2334 for the vertical axis. 



CALC-SPAR CRYSTALS FROM SOUTH AFRICA. 



The cleavage rhombohedron of Calcareous Spar, in simple crystals, is well 

 known to be exceedingly rare. As truly stated by M. Dufrenoy, the simple 

 rhombohedrons often labelled " calc-spar" in collections, belong, in general to 

 Dolomite. The writer of these notes, however, has lately received with other 

 minerals from Namaqualand, in South Africa, several large crystals of calcareous 

 spar, occurring in - the simple cleavage form. Most of these crystals are some- 

 what distorted by elongation, and all are striated on the surface in the 

 direction of a plane at right angles to the vertical axis. They are associated with 

 trap, or trap tufa. 



In the dolomite rhombohedrons, the obtuse angle over a polar edge, equals 

 106° 15'; and the presence of magnesia may be readily detected by dissolving 

 the substance in a few drops of diluted hydrochloric acid — adding a drop of nitric 

 acid, and boiling (to convert any Fe O that may be present, into Fe 2 0s) — and 

 precipitating by ammonia and oxalic acid the iron (if present) and the lime. The 

 magnesia can then be thrown down from the filtered solution, by phosphate of 

 soda, and tested with nitrate of cobalt before the blowpipe. If conducted in 

 test-tubes, and on small quantities, the whole process need not occupy more thau 

 ten minutes. 



The following logarithmic formula (extracted from some notes by the writer, in 

 the Phil. Mag. of August, 1853,) for the determination of the vertical axis in 

 rhombohedrons, may not be unacceptable to some of our readers : — 



Let a = half the inclination, as obtained by measurement, over a polar edge ; b, 

 the inclination of a rhombohedral face on the vertical axis ; and v, the axial length 

 required. Then : 



Log cos b = log cos a + 0.0624694 ; 

 Log v = log cot 6—10.0624694. 



E. J. 0. 



PHYSIOLOGY AND NATURAL HISTORY. 



CANADIAN STRIGIDAE. 



In communicating the following notes on the Canadian Strigidae, the object it 

 mainly to procure information. Nevertheless, those who have not studied the sub- 

 ject may be interested in learning how many varieties of these curious and remark- 

 able birds frequent the neighbourhood of Toronto ; as well as in knowing that a 

 tolerably complete collection of specimens of them have been admirably preserved 

 for the University Museum, by the late Mr. Hadgraft and Mr. Passmore, and can- 

 not but prove attractive to every lover of natural objects. It is not, perhaps, 

 presuming too much to hope that intelligent and scientific gentlemen of this 

 district, on observing what has been already procured will use their endeavours to 

 extend the list and assist in obtaining the few other species still wanting, 

 among the more familiar examples, or any novel or rare forms which may 

 present themselves. 



