PAKT 1 .] 
Annnal Jleporl for 1878. 
a 
When, therefore, a stone imjjlemeut was found in these gravels, it was made the 
occasion of a special consideration of some features of the case that had not pre- 
vioiisly been discussed. This proceeding was no more than was demanded by the 
peculiar interest of the occasion. The same judicious caution has markedly 
characterized the most recent investigations by perfectly impartial observers 
regarding the human period in England. 
PenijigulciT area,: Azoic Tocks —To follow the order observed in the Manual, 
the azoic rocks are noticed first. The Arvali region is tho only ground where we 
have been especially engaged upon these formations during the past season. 
!Mr. Hacket examined a very largo area at the northern extremity of the range, 
with all the outliers between Decg and Tosham (near Hiinsi), up to tho Jumna 
at Delhi. Mr. Hacket has hitherto had this area all to himself, and at pages 48 to 
52 of the klanual an abstract is given of the provisional views then suggested. 
Very considerable changes in the stratigraphical series are now proposed. Tho 
klandan and Ajabgarh groups, lying mainly to the west of the Alwar and Delhi 
range of quartzites, were placed at the top of the series. The Mandan rocks occur’ 
in isolated ridges, and were separated from tho Ajabgarh beds on account of tho 
absence of certain bands that arc prominent in tho latter group; while tho 
Ajabgarh beds were placed above the Alwar quartzites on account of some cases 
of steep, partial superposition which must now be regarded as inversions, for 
Jfr. Hacket considers both the klandan and Ajabgarh beds to be representative of 
the Raiiilo group, underlying the Alwar quartzites. In the study of extensive 
areas of contorted transition rocks, tho tendency is usually towards a greater sub- 
clE'ision and expansion of the series, original features of unconformity being 
often disguised by the crushing of the strata; but Mr. Hacket makes out a good 
ca.se for this contraction of the Arvali series, as first proposed. The very mixed 
and variable character of the deposits of the Raialo group was pointed out fi’om 
the first; and in this as well as in other petrological characters the agreement 
of the Mandan and Ajabgarh rocks is sufficiently close, besides that now sections 
have shown these to have the same relation as the Raialos to the gneiss and to the 
Alwar quartzites. 
The adoption of two instead of four groups is, so far, an apparent simplification ; 
but the chief structural difficulties of the ground are still unexplained. These 
are, the almost incompatible variations in the relations of these groups to each 
other and to the gneiss. In many sections the two groups are described as com¬ 
pletely transitional, by interstratification. Again, each group is locally described 
as transitional with the gneiss : tho Kaialo black slates passing down into a dark 
schistose gneiss; and the Alwar quartzites being transitional downwards with a 
gneiss that is only a subfoliated felajjathic quartzite, liut in other sections tho 
Alwar quartzite is described as overlapping on gneiss, as in tho hills between Udepur 
and ^Khandola, 40 miles noi’th-wost of Jejqoore. These discrepancies might be 
got over by assuming that all the gneiss is simply converted Arvali strata, the 
metamorphism having extended locally to different horizons; and that the word 
‘ overlap’ is misapplied in such cases, for it implies a primitive gneiss, with 
original local absence of the Kaialo group ; and no distinction of gneisses has been 
