1880.] > Spill i (Diller. 
that such beds do not occur. The line of contact between the fel- 
sites and the southern side of the stratified group is covered through- 
out its whole extent, and I have not been able to find the two rocks 
along the line, exposed nearer together than at the locality named. 
North-east of Oakland Vale, along the northern border of the 
stratified group, a white quartzite, and dark slightly porphyritic 
felsite with distinct fluidal lines, occur within ten feet of each other. 
The line of contact is covered, but as in the other case, there is no 
sign of transition. We hope to find an exposed junction of the two 
rocks, and thus by direct evidence prove their relation. 
Mr. Crosby in his report upon the “ Centennial Map” page 17, 
speaking of the porphyritic felsite of Malden, Melrose, Saugus, and 
Lynn says :—“ going northward in Melrose the porphyritic charac- , 
ter gradually disappears, the felsite becomes more silicious and grad- 
ually becomes interstratified with quartzite and hornblende slates. 
The transition is so gradual that it is impossible to define the bound- 
ary between the stratified and unstratified felsites, which proves 
there is no break, no natural division here.” 
After reading the above statement, I carefully examined the rocks 
referred to, and must beg leave to differ with Mr. Crosby in every 
particular named. The most completely porphyritic felsite I have 
seen anywhere occurs near the south-west corner of Long Pond in 
Melrose, close to the stratified group where it is cut by the granite. 
The porphyritic character varies in the Malden Highlands, but there 
is no gradual decrease northward, as this suite of specimens plainly 
shows. The basic felsite along Washington street is just as porphy- 
ritic as that along Highland avenue or Salem street; but when we 
pass several hundred feet northward from the foot of the Highlands 
to the stratified group, we find rocks fundamentally different from 
those of which the Highlands are composed —rocks without the 
slightest porphyritic structure, and instead of the fluidal line of the 
felsite, they contain distinct lines of sedimentation. 
Conclusive evidence as to the relation of the stratified group and 
felsite is found also in the relations which the two hold to the 
granite. It has already been shown that the stratified group is older 
than the granite, and that the felsites are younger than the granite. 
The felsites and the stratified group are undoubtedly distinct for- 
mations in nature, notwithstanding the numerous statements of emi- 
nent authorities to the contrary. 
