246 Transactions of the Royal Microscopical Society. 
ing to the modern “ greystones” of Scrope or trachy-dolerites, and 
now I think there is equal reason to believe that at that very 
remote geological period, the Lower Silurian, there were erupted some 
lavas also of a basaltic type, and therefore that the idea formerly 
held of the specific distinctness of the ancient from the modern 
voleanic rocks is one that cannot be sustained. Mr. Allport has 
already shown the specific identity of Carboniferous dolerites and 
basalts with those of modern date, and I think that the microscopic, 
chemical, and field evidence which I have been able to collect among 
the volcanic rocks of the Lake district almost as clearly proves the 
existence of doleritic and trachy-doleritic lavas among the Lower 
Silurians. ' 
ANALYSES OF CUMBERLAND LAVAS. 
(1) (2) (3) (4) (5) ‘ 
Brown | tron Cr ag Dolerite. 
Knotts (Keswick Eycott Eycott Eycott Mean 
Sortie District). Hill. Hill. Hill. Analysis. 
Silica... .. .. «. | 60°718 | 59°511-| 53°300 | 52°600 | 51-100 | 51-00 
Alumina .. .. .. | 14°894 | 17°460 | 20°990 | 17°315 | 22-051 | 16°06 
OLA ies! ess ieee 2°354 | 3°705 °926 | 1°486 | 1-022 “84 
Soda .. ; 2°843 | 3°093 | 2°456 | 2-622) 2-216 2°66 
1 LTC Le rae Pe Oe 6°048 | 5°376 | 8°512 | 7-728 | 11:424 9°53 
Magnesia... <5 0% 1:909 |} 1°801 | 3°964 | 3°252 | 2°346 5°18 
Ferrous oxide .. 6°426 | 4°926 | 6°343 | 12-043} 5-885 14°75 
Ferric oxide .. .. | 1°405 | 1°271| 1:°660| 1°722| 1-210 \ ? 
Bisulphide of iron .. *395 “604 
Phosphoric acid ., "281 "115 *102 +153 “179 
Subphuricacid.. .. 103 "086 | trace trace trace 
Carbonic acid .. .. 1-660 | 1°569 *320 -140 | 1:°820 
Loss on ignition .. 964 °483 | 1-120} 1-160 -710 1-42 
100°000 |100°000 |£00-000 |100-000 |100-000 
Nos. 1 and 2 have been already published in the memoir on the Keswick dis- 
trict (sheet 101 8. E). Nos. 3, 4, and 5 are new, and unpublished in any paper 
or memoir. 
