20 



Amongst the properties of spherical curves, the following curious 

 Olio occurs. 



If the pole of a loxodrome to rhumb « be made the centre of 

 another equal sphere, the visual cone under which the loxodrome will 

 appear, will cut the second sphere (the eye being at centre of first 

 sphere) in a curve, whose equatorial subtangent is constant, and 

 equal to « : and if conversely, the pole of the spherical logarithmic 

 (the equisubtangential curve just mentioned) be made the centre of 

 an equal sphere, the visual cone of this logarithmic, seen from the 

 centre of its own sphere, will cut the second sphere in a loxodrome 

 whose rhumb is equal to the subtangent of the logarithmic. 



The author expresses his intention of discussing in a separate 

 work the singular points of spherical curves, certain new systems of 

 co-ordinates, and other classes of research, which, on account of the 

 length to which they necessarily extend, were not adapted to the 

 Transactions of the Royal Society. 



3. Experiments and Observations on the Arterialization 

 of the Blood. By William Gregory, M.D., F.R.S.E., 

 and W. J. Irvine, Esq. 



The object of these experiments was to ascertain some of the cii'- 

 cLiinstances under which the blood changes in colour, from the dark 

 venous to the florid arterial hue. 



Dr Stevens first showed, that the venous clot deprived of its serum 

 by washing, remained dark even when in contact with oxygen ; and 

 that the addition of a saline solution caused it immediately to become 

 florid. He stated also, that a strong saline solution would cause this 

 cliangc in an atmosphere so highly chai'ged with carbonic acid as to 

 prove lapidly fatal to animals. 



It appeared to the autliors necessary to ascertain whether this 

 effect took place in pure carbonic acid containing no free oxygen, as 

 the atmosphere used by Dr Stevens most probably did; and they 

 also proposed to extend their observations to other gases, likewise 

 free from oxygen. They accordingly prepared pure nitrogen, hy- 

 drogen, and carbonic acid, removing the last traces of oxygen by 

 means of potassium. The water with which the clot was washed, 

 and the saline solution used in the experiments, were deprived of at- 

 mospheric air by being boiled and allowed to cool in close vessels. 

 The clot was then introduced into the gases over mercury, and as 

 soon as the strong saline solution came in contact with it, the colour, 

 in all the three gases, changed from black to bright red., and the 

 same change was found to take place in the Torricellian Vacuum. 



