Reviezv of Recent Geological Literature. 319 
The Structural Relations of the Amygdaloidal Mclaphyr in Brookline, 
Newton, and Brighton, Mass. By H. T. Burr. (Bull. Mus. Comp. 
ZooL, vol. xxxviii. Geol. Ser., vol. v., no. 2, pp. 53-69, 2 pis.) 
In earlier years, the melaphyrs of the Boston basin have been con- 
sidered as contemporaneous flows by some writers. The present paper 
appears to prove beyond doubt that those of the western portion, in- 
cluded in the above-mentioned territory, are entirely intrusive. We 
have no fossiliferous horizon to use as a key to structure ; and the 
presence of contemporaneous flows would be welcome. Their proved 
absence in the western areas removes that aid, as far as those areas 
are concerned. Readers who are familiar with the geological literature 
of the region know the general relations of the rocks as regards posi- 
tion, and it is not necessary to state them here. 
A word may not be out of place, concerning the methods used in 
this study, which was an incidental one ; for they illustrate the careful 
approach which is now employed in the problems in this difficult field. 
A detailed outcrop map was plotted on a very large scale, made possi- 
ble by the aid of city engineers. This gave the exact location of every 
exposure of melaphyr, and of the other rocks as well. Detailed obser- 
vations were recorded for each outcrop, and specimens collected when 
necessary, for petrographic work. The result appears in the character 
of Mr. Burr's paper, which is a mass of clearly presented evidence, 
with the inevitable conclusions drawn from it. The former is so stated 
that the precise outcrops are indicated, and one can without difficulty 
prove the worth of the observations for himself. This is as it should 
be. 
The evidence is of three kinds : lack of melaphyr pebbles in the 
overlying conglomerate, negative but confirmatory ; character of the up- 
per contacts of the melaphyr; and structural relations. The summary 
ii worth giving in full, "(i) The melaphyr, in the region discussed, 
is intrusive in the sediments. (2) The melaphyr is not associated with 
any definite horizon, and is therefore of no value as a guide to the in- 
terpretation of the structure. The first conclusion depends upon the 
following facts: i. The conglomerate, associated with the melaphyr, 
contains no fragments of it. 2. The contacts, wherever found, are ig- 
neous in character. 3. The melaphyr is seen in contact with sediments, 
varying from the coarsest of the conglomerates to the finest of slate. 
4. The distribution of the melaphyr shows it to be discordant with the 
structure of the sediments under any interpretation of the latter that 
has been offered. The second conclusion follows directly upon the 
first." 
While these problems occupy most of the paper, space is given to a 
new interpretation of the structure of the Chestnut Hill slates and the 
northern conglomerate, which harmonizes with the field evidence better 
than any of the earlier views. j. e. w. 
