Bemains of the Rein-deer in Scotland. 137 



same alluvial deposits, as that in which the remains of the 

 rein-deer were found. In the year 1848, four canoes were 

 found at Springfield, and all of them within a few yards of 

 each other. These canoes were covered hy a deposit of 

 17 feet of finely laminated sand. In other cases canoes 

 have been found in the same alluvium, but much farther in- 

 land or remote from the modern channel of the river, as at 

 London Street, and under the site of St Enoch's Church, and 

 in the two last quoted instances the canoes are probably of 

 greater antiquity than the remains we have described. 



On certain New Applications of Prisms. By the Rev. W. 

 Hodgson, Old Brathay, Ambleside. With a Plate. Com- 

 municated by the Author. 



It has long been well known that when objects are viewed 

 by means of pencils of light, which are refracted through an 

 isosceles prism, and suffer an internal reflexion at the base, 

 the objects are seen quite free from chromatic dispersion. 

 Little attention however seems to have been paid to the fact 

 that there is a position in which the pencils of light, after 

 being thus refracted and reflected, may be made to enter the 

 eye along with other pencils proceeding directly from the 

 object. The position referred to is that represented in figure 

 1. If P Q and P E be contiguous rays of a parallel pencil 

 proceeding from a distant object, one ray will follow the 

 course P Q R S E, while the other will pass directly from 

 P to E. In this position the image and the object coincide 

 exactly ; but if there is the slightest deviation from this 

 position on either side, then the object and the image may 

 be seen separately. 



The application of this principle to the measurement of 

 angles is easy and obvious. For this purpose the prism 

 merely requires mounting, with its axis perpendicular to a 

 movable graduated circle, which is capable of being adjusted 

 at any required inclination to the horizon. 



The form of prism best adapted for an instrument of this 

 description seems to be one of which the principal section 

 is an equilateral triangle. For as an observation can be 



