128 REPORTS ON THE STATE OF SCIENCE.—1912. 
This is one of the rocks composed of purple phyllite rapidly alter- 
nating with bedded jasper. Both types are included in this analysis, 
but there is more of the jasper than of the phyllite. 
770 A. Traeth Dynion, Amlwch. (Fissile part of Amlwch schist.) 
i: II. 
oo aed a I pO es ees | 3-63 
Nal =, et. . a. Se 2-96 
This is the fissile pen that oe el of the Amlwch schists, corre- 
sponding to the similar part of the schists of Holyhead. The hard part is 
really fine grit, but has not yet been analysed. 
741 A. Variolitic Pillowy Diabase, Amlwch. 
I. O. 
SiO, 39°18 39°22 
5 2°21 2-20 
Al,O, 18°81 18°79 
Fe,0, 8-62 8°61 
FeO 4:99 5°01 
MnO Nil Nil 
CaO 9°70 9°69 
MgO 10°02 10°05 
K,O 0-18 0°15 
Na,O ‘ : ; : : ; 3 ‘ 1°87 1°89 
H,0 (at 110°) 5 OY AES poh MMe Fk Jahier FORD 0-10 
H,0 (above ii0*) RD Sate Pac en it eg te Mae i Ss 4°54 
100-20 100-25 
This rock should be compared with the similar rock analysed some 
time ago ard published in a former Report. The types differ consider- 
ably. 
Cf. 82 A. Holland Arms Railway pais Dolerite. 
Steet, Ss ry cy ee 46-46 
This is from the Holland Anne Main Dyke, one of the later dykes 
of the island. 
Specific gravities have been taken of the following basic dykes, and 
also of two other basic rocks :— 
Specific gravities. 
Holland Arms Main Dyke eps Atiene tte daettion il) dae 
Holland Arms Minor ,, ‘ ‘ ‘ : : 5 : . 2-852 
Plas Newydd es : 3 : é ; é 4 . 2-966 
Graig Fach on 2 js F . 5 5 F . 2-948 
Garth Lodge x5 , 3 . é 3 . 2-785 
Pont Dick s , 4 ; ; g S : . 2-987 
Castellor 3 ‘ : : ; : : : . 2-985 
Yr Allt be ie Th Slee Ae me 
Mynydd Mechell (a) __,, anaes ere WO Orme Ss 
Mynydd Mechell (6) _,, Sf) tl OS eens ae coe 
Wylfa 3 Rie yee ae ae ne Wr en 
Pillowy Diabase, Cerig Chiirin. "2 Wh ayers, eee Se 2-825 
Dolerite, Three Lakes. 2 GOs Be Soda “Ve oe 
Most of the rocks that have been analysed have been from the great 
schistose complex. Some from other systems have also been selected, 
