358 On the Colour of the Atmosphere and Deep Water. 



ter which it descends obliquelyj probably to the bottom of the 

 sea, where the eyes cannot follow it beyond 30 or 40 feet. 



This construction gives an immense opening for the light to 

 penetrate into the grotto across the water, even when the small 

 opening above the level of the water is closed, and thus occa- 

 sions, in a great mass of water, that dispersion of the blue ray 

 which always takes place in deep and limpid waters, and which 

 appears most conspicuously in the azure grotto, because it is not 

 mingled with any other light.* 



After having considered the opaline property of the air and 

 waters, let us make some inquiries into the production of opa- 

 Hne blue in opaque bodies. 



We have formerly mentioned the blue tint observed in the 

 fine skin with which the veins are covered. Leonard de Vinci 

 alludes to this phenomenon, which is entirely owing to the opa- 

 line property of the skin. Let us examine the conditions neces- 

 sary to produce it. 



( To be concluded in next Number. ) 



NOTICE OF BOTANICAL EXCURSIONS INTO THE HIGHLANDS OF 

 SCOTLAND FROM EDINBURGH THIS SEASON, 1833. By 



Br GrabjM.,^ ' ' ' " 



In the end of June, Mr Brand, Mr Munby, and Mr James 

 Macnab, spent a few days in Clova, and found, in addition to 

 the plants already known as natives of that interesting district, 

 Arbutus alpina, on the top of the mountain opposite to the vil- 

 lao-e of Kirkton. This is an unexpected addition to the Flora 

 of that range, and shews still further the impropriety of hastily 

 discarding from the natives of a particular district, plants which 

 have not recently been found in it ; for I feel convinced, that I, 

 and others, have passed within a few yards of the station where 

 these gentlemen found the Arbutus, yet never saw it there. 



Favoured with the company of a number of friends, devoted 

 to various branches of natural history, and some of them emi- 



• It may be recommended to travellers to examine the colour of the wa- 

 ter in our sea-caves, particularly those on the coast of Sutherland, some of 

 which have the situation, form and dimensions of the azure grotto of Capri. 

 — Edit. 



