202 J. H. A. Whealler—Boulders of Cambridge Gravels. 
made by Rastall and Romanes, no less than six boulders were 
found bearing a strong resemblance to them. They were collected 
from the following localities :— 
(a) Two from fields north of the Madingley Road, 5 miles from 
Cambridge. 
(b) Gravel pit, Milton Road. 
(c) Deep Spring Biddenham, Bedfordshire. 
(d) Two found east of the * Golden Lion ” , Kingston. 
Sirna is in the Dala district a few miles from Elfdal itself, and 
about 200 miles north-west of Stockholm. The presence of Dala 
boulders in England has (according to Milthers) been reported rather 
indefinitely before.? 
The important Swedish indicator boulder—the Scanian basalt— 
has not been definitely found at the pit, but basalts are extremely 
common, and, owing to the multiplicity of Scottish types and the 
similarity of basalts generally, no definite results have been obtained. 
Three interesting nordmarkites were collected last year. One 
on a heavy mineral separation yielded a quantity of copper; 
the other two were sliced, one having a special peculiarity im that 
riebeckite is developed instead of arfvedsonite, and the other shows 
strong affinities to this rock. 
Three extremely interesting boulders were . collected last year, 
all probably Scandinavian, but their exact locality is uncertain. 
The first type has been found twice and is a porphyry with extremely 
fine felspar phenocrysts up to 10 mm. in length, and showing intact 
crystal faces; the greyish-white groundmass contains abundant 
green specks which on microscopic examination proved to be 
egirine. The second specimen is a gabbro with some affinity to 
the essexites: 1t contains some orthoclase, and the uralitic horn- 
blende is blue in places, showing derivation from a soda-bearing 
augite. The other rock was collected as a largish boulder, and is 
a syenite with lepidomelane, and was found, when a slice was 
examined, to contain barkevikite. Neither this ‘rock or the eecirine- 
porphyry could be matched in the collection of Scandinavian rock- 
types at South Kensington Museum. 
The complete’ list of Scandinavian types which have been 
recognized at the pit may be summarized thus :— 
Swedish.—Sarna porphyry and related types. 
Norway: 1. Rhomb-porphyry. 
2. Laurvikite. 
3. Christiania soda granite. 
4. “* Copper-bearing ”’ nordmarkite. 
5. Riebeckite-nordmarkite. 
6. Nordmarkite showing affinities to No. 5. 
Doubtful : Barkevikite-syenite. 
A{girine-porphyry. 
1 Indicator Boulders and V. Madsen, Quart. Journ. Geol. Soc., vol. xlix, 
1893, p. 114. 
