NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
Note regarding certain characters in the Subsoil of Calcutta.
BY
SURGEON-MAJOR D. D. CUNNINGHAM, M.B.,
SPECIAL ASSISTANT TO THE SANITARY COMMISSIONER WITH THE GOVERNMENT OF INDIA.
The scheme for the construction of a dock at Kidderpore, one of the
suburbs of Calcutta, has afforded special facilities for acquiring information,
both in regard to the nature of the subsoil and the extraordinarily incorrect
ideas which are commonly entertained regarding it. When the question of
the construction of the dock was still under consideration, it was authoritatively
announced that the subsoil in which it was intended to lay the foundations
consisted of "blue clay," that it contained no subsoil water, and that its im
-permeability almost equalled that of cast-iron, so that no accumulation of water
would ever occur in the excavations necessary for the construction of the
dock beyond that due to direct rainfall so long as means were taken to exclude
surface drainage. Having for many years had special occasion to consider the
nature of the subsoil in Calcutta, I entertained great doubts as to the correct
-ness of these statements, and accordingly tried a series of experiments with
the view of obtaining actual data in place of "speculative opinions," as the
advocates of the dock-scheme styled all views which tended to cast any doubt
on the impermeable nature of the soil. The present note contains an outline of
these experiments, the result of which was to show clearly that the so-called
"blue clay" is not clay at all, and that, in place of being impermeable, it
contains a very high proportion of air or water content according to the
conditions to which it is exposed.
The materials experimented with consisted of samples of the "blue clay,"
one obtained from a member of the Committee which was appointed to enquire
into the sanitary aspects of the dock-scheme, the other procured by myself
from the bottom of the initial excavations for the dock-walls. Both were
precisely alike, consisting when first obtained of a slate-coloured, rather evil-
odoured, dense, moist substance, permeated in many places by channels partly or
wholly filled with soft brownish matter and corresponding with the sites at
one time occupied by the smaller roots of trees, which formerly grew on the
present subsoil, and whose remains occur in abundance in it. On keeping
the material, it rapidly parted with its moisture, becoming, as it did so, of a pale
grey colour and hard consistence. Specimens were submitted to analysis
D
Scientific Memoirs by
both in the laboratory of the Assay Department of the Calcutta Mint and
in that of the Chemical Examiner to Government with the following results :—
(I) Analysis in the laboratory of the Assay Department, conducted by
elutriation on samples which had been submitted to prolonged drying
a t 1 0 0°C. —
Sand . . • . • . • • • 15. 55%
Being fine sand . . .
46.86%
Organic and volatile matter .
• • • 7.36%
Clay . . . . . . . . . 30.2 %
(2) Analysis in the laboratory of the Chemical Examiner to Government
Moisture ..
.
. .
18.o6%
Organic matter .
. . .
.
3. 76%
Silica. .
.
.
..
. . 58. 31%
Oxide of iron.
• • . 8.66%
Alumina
. . . •
Lime and magnesia, a trace.
11.21%
It might at first sight appear as though the two analyses gave discordant
results in regard to the proportion of clay present in the soil. This, however,
is a mere matter of appearance, and is due to the fact that the method of
determination was different in the two analyses. In the first the method
employed was that of elutriation, which is a mechanical process of " separation
of substances by washing them in large quantities of water, so that the heavier
particles fall to the bottom, and the lighter ones, remaining some time suspended,
are gradually deposited in a finely-divided state" What in it is styled clay is
not, therefore, equivalent to chemically pure clay, but merely to a mass of very
finely-divided particles to which the term mud would have been more strictly
applicable. In the second analysis the method followed was the ordinary
chemical one, and the proportion of clay is indicated by the amount of alumina.
Even, however, were we to accept the mud of the first analysis as equivalent
to clay, which it certainly was not, the soil could not be correctly described as a
clay one. In Morton's Cyclopædia of Agriculture we find the following state
-ments regarding the classification of soils :
— Soils in general consist of a mechanical mixture of the following four ingredients :
—
1 . S i l i c a , s i l i c i o u s s a n d , a n d g r a v e l .
2 . C l a y .
3 . L i m e .
4 . A n i m a l a n d v e g e t a b l e r e m a i n s ( h u m u s ) .
There are few soils which consist of only one or two of these four substances ; most
contain them all, but the relative proportion of each in different soils varies considerably,
A natural division of soils, accordingly, may be founded on the preponderance of one
of these four chief constituents.
Upon this principle, soils may be conveniently classified as follows :
— 1. Sandy soils, containing above 80 per cent. of silicious sand.
2. Cal car eous soi l s, cont ai ni ng above 20 per cent , of l i me.
A Di cti onary of Sci ence, Li terature, and Art, by Brande and Cox, 1872, p. 770.
Medical Officers of the Army of India .
21
duced. On the following morning the cavity was found to be quite empty, the
surface being still moist, but with superficial cracks on it. During the course of
t h e f o r e n o o n 1 7 5 c . c . o f w a t e r d i s a p p e a r e d f r o m t h e c a v i t y , a n d t h e e x p e r i m e n t
was brought to a close by one-half of the moist block, which was only supported
centrally by an iron tripod, breaking away, due to its own weight. During the
period of experiment 350 c.c. of water had disappeared from the cavity, and
only 6 c.c. from the glass vessel as the result of evaporation, leaving 344 c.c.
to be credited to the permeability of the soil. This amount does not fairly
represent the entire loss possible for the entire period, as the block was only
under observation during the hours from 7 A.M. to 7 P.M. daily and the cavity
had evidently remained empty for a long time between the experimental periods
of the two successive days.
A second experiment of like nature was conducted as follows. The block
of soil in this instance measured 19 c. in length, 12.7 c. in breadth, and 7.1 c. in
depth, and was supported beneath on a piece of wire gauze, so as to avoid
chances of breakage like that of the previous experiment. The cavity in it and
the glass vessel used to determine loss by surface evaporation were of the same
character as in the previous case. Daily additions of water were made to the
cavity on all those days on which the laboratory was open during the hours in
which it was under observation—from 7 A.M. to noon or to 3 P.M. in one or two
instances. The experiment lasted for nineteen days, the water in the glass vessel
having totally disappeared by evaporation on the morning of the twentieth day.
The amount of water added daily to the cavity for the period was as follows :—
Date.
Day of
Experi ment.
Amount of Water added.
May 13th . 1st . . 138 c.c.
„ 14th . 2nd . . 135 c.c.
„ 15th . 3rd . . 125 C.C.
„ 16th . 4th . . 161 c.c.
„ 17th . 5th . . ... Laboratory closed.
„ 18th . 6th . . 116 c.c.
, ,
1 9 t h
. 7th . .
1 1 1
c . c .
„
2 0 t h
. 8th . . 124 c.c.
, ,
2 1 s t
. 9th . . 103 C.C.
, ,
2 2 n d
. 10t h
104 c.c.
, ,
2 3 r d
.
1 1 t h 103 c.c.
„ 24th . 12th . .
. . . Laboratory closed
,, 25th . 13th . .
. . .
,, ,,
„ 26th . 14h . . 155 c.c.
, ,
2 7 t h
. 15th .
1 1 0 C . C .
„ 28th . 16th . . 85 c.c.
, ,
2 9 t h
. 17th . . 105 c.c.
„ 3oth . 18th . . 97 c.c.
„ 31st . 19th . . . . .
Laboratory closed.
June 1st . 20th . .
. . . Glass vessel empty.
22
Scientific Memoirs by
During this period 1,772 c.c. of water had disappeared from the cavity in
the soil and 75 c.c. from the glass vessel due to evaporation, leaving a loss of
1,697 c.c. to be credited to the permeability of the soil. The entire cubic
capacity of the block of soil minus the cavity was 1,635.5 c.c., and hence during
the period a bulk of water had disappeared from the cavity due to percolation
greater than the bulk of the entire block into which it was absorbed. The
results moreover, as in the previous case, by no means represent the total
absorptive power of the mass of soil for the period, as the cavity was almost
always empty for a considerable period daily and on some occasions remained so
for entire diurnal periods.
A third experiment was now tried with the same mass of soil and only differ
- i n g f r o m t h e p r e v i o u s o n e i n t h a t a g l a s s c y l i n d e r o p e n a t b o t h e n d s w a s f i t t e d
accurately into the interior of the cavity, any small interspaces between the
glass and soil being filled with firmly rammed material, so as to secure accurate
contact everywhere. The cavity in this case thus differed from those in the
previous ones in having impermeable walls, so that water could only come into
contact with the soil of the floor. The experiment lasted from the 1st to the
29th June with the following results
Date.
Day of
Experi ment.
Amount of Water added.
June 1st 1st
150 c.c.
, ,
2nd . 2nd . . 140 c.c, Cavity quite empty in the morning.
„ 3rd . 3rd . . 125 c.c. , , , ,
, , , , , ,
„ 4th . 4th
. 120 c.c. , , , ,
, , , , , ,
„ 5th . 5th . . 118 c.c. , , , ,
, , , , , ,
„ 6th . 6th . . 118 c.c
, , ,,
, , , , , ,
, ,
7th
7th
. ... Laboratory closed.
„ 8th . 8th . . 124 c.c. Cavity quite empty in the morning.
„ 9th . 9th . . 118 c c.
„ 10th . 10th . . 119 c.c.
„ 11th .
1 1 t h
. . 118 c.c.
„ 12th . 12th . . 108 c.c.
, ,
13th . 13th . . 115 c.c.
, ,
14th . 14th . .
. . . Laboratory closed.
, ,
15th . 15th .
107 c.c. Cavity quite empty in the morning.
, ,
16th . 16th . . 91 c.c. Cavity contained a little water in the morning.
, ,
17th . 17th . . 82 c.c. , ,
, , ,,
, ,
, , , ,
, ,
18th . 18th
. 75 c.c. , ,
, , , ,
, ,
, , , ,
, ,
19th . 19th . . 69 c.c. Cavity contained some water in the morning.
, ,
20th . 10th
. 61 c.c.
, ,
21st . 21st . . . . .
Laboratory closed.
, ,
22nd . 22nd . . 90 c.c. Cavity quite empty in the morning
„ 23rd . 23rd . . 64 c.c. Cavity contained some water in the morning.
, ,
24th 24th • . 50 c.c. , ,
, , , ,
, ,
, , , ,
, ,
25th . 25th . . 39 c C.
, ,
, , , , , ,
, , , ,
, ,
26th . 26th . . 43 c.c. , ,
, , , ,
, ,
, , , ,
, ,
27th . 27th . . 46 c.c
, ,
, , , , , ,
, ,
, ,
28th . 28th . . ... Lagoratory clo
sed.
„ 29th . 29th
. 72 c.c.
Medical Officers of the Army of I ńdia.
23
The glass capsule registering loss by evaporation from a surface equal to
t hat present ed by t he cavi t y had l ost 60 c. c. of wat er duri ng t he peri od. The
total loss from the cavity in the same time was 2,362 c.c. or 2,302 c.c. due
to the permeability of the soil. The diminution in daily loss from the cavity
coincident with the great increase in atmospheric humidity attendant on the
onset of the rainy season comes out very distinctly. During the entire course
of the previous experiment and in the early part of the present one the surfaces
of the block of soil appeared continuously dry, but when the atmospheric humid
-ity increased and the disappearance of water from the cavity conspicuously
diminished, the surfaces became evidently and constantly moist. Another phe
-nomenon, common to this and the previous experiments, but which came out
most conspicuously here, was the gradual diminution in the capacity of the
cavity due to the disintegrant action of the water on the soil. The floor of
the cavity was originally flat and flush with the lower edge of the glass cylinder
which formed its bounding wall. As time went on, however, it gradually swelled
up and in place of consisting of the dense material of the mass in its original
condition came to be composed of soft, loose mud derived from the disin
-tegration of the soil at the base of the cavity and from beneath the edge of the
cylinder, which ultimately, in place of resting on the firm soil, was suspended
over this soft, incoherent substance.
Another experiment of a different nature was tried. In it a long glass tube
was rammed with some of the soil which had been previously dried over a gas
flame and thoroughly triturated. The rammed soil occupied 66c. of the length
of the interior of the tube. The tube was fixed in a horizontal position with
one end connected with the lower extremity of a glass receiver full of water, and
the other with an open U-tube containing fragments of chloride of calcium.
The experi ment was i ni t i at ed on t he 20t h May by openi ng t he t ap at t he
bottom of the receiver and allowing the water to pass into the tube. The water
advanced along the portion of the tube occupied by the soil at a rate shown by
the following figures :—
Date.
Extent to whi ch water had evi dentl y
advanced al ong the soi l .
May 21st .
18.6c.
, , , 22nd
24.5c.
„ 23rd ..
2 9 . I c .
, , 26th .
37.5c.
, , 27th.
3 9 . 6 c .
, , 28th . .
4 1 . 2 c .
„ 29th. .
„ 30th .
4 4 . 5 c .
June 1st ..
4 6 . 9 c .
, , 2nd.
24
Scientific Memoirs by
Date.
Extent to whi ch water had evi dentl y
advanced al ong the soi l .
June 3rd ..
51.7c.
„ 4th . .
52.1c.
„ 5th .
52.2c.
, , 6th . .
53.05c.
, , 8th . .
54.6c.
„ 9th..
55.2c.
, , 10th .
56.9c.
, , 11th ..
57.4c
, , 12th .
58.9c.
, , 13th
59.0c.
,, 15th ..
61.4c.
„ 16th ..
62.9c.
„ 17th. .
63.4c.
„ 18th. .
64.2c.
„ 19th .
66.0c.
From the above figures it appears that the water took 30 days to traverse
a stratum of soil 66.c. thick, and closed, save at its extremities, by an impermeable
material. Subsequent to this slow percolation continued to occur as indicated
by the gradual accumulation of a considerable quantity of water within the
distal portion of the tube beyond the soil.
The above experiments appear to demonstrate sufficiently clearly that the
subsoil in Calcutta is just as little " impermeable" as it is " blue clay," and
it now only remains to attempt to find an explanation for the erroneous ideas
prevalent in regard to its nature. The peculiar colour of the material, its con
- s i s t e n c e w h e n f r e s h l y e x c a v a t e d a n d m o i s t , a n d i t s s t o n y h a r d n e s s o n d r y i n g
are perhaps enough to account for the popular description of it as consisting of
" blue clay." It is, however, at first sight, difficult to understand on what the
idea of its impermeable nature was founded, seeing that it must have been
patent to the most casual observation that in its normal site it included a very
considerable amount of water content and that it parted with this with great
readiness on exposure to sunshine and dry air. The belief must apparently
have been due to the fact that, whilst really containing a very large amount of
air or water space, the soil is yet so fine as to prevent rapid transit of water
under ordinary circumstances. Excavations made in a soil of this character
will, of course, not be liable to contain conspicuous accumulations of percolated
water so long as evaporation is taking place with any considerable activity from
the exposed surfaces. The last of the experiments on the permeability of blocks
of the soil affords a direct proof of this, for in it it was only with increased
atmospheric humidity and diminished recipient power in the soil that the sur
- f a c e s b e c a m e c o n s p i c u o u s l y m o i s t . I n t h e l a b o r a t o r y i n w h i c h t h e e x p e r i m e n t s
were conducted there was a regular daily loss of 0.125 of an inch in depth from
Medical Officers of the Army of India.
25
exposed surfaces of water until the rise of atmospheric humidity set in, although
the water was never exposed to direct sunshine and for the greater portion of
the diurnal period was in a closed room absolutely protected from the influence
of wind. The evaporation from surfaces freely exposed to sun and wind must,
of course, be much greater under otherwise like conditions. A series of experi
-ments on bodies of water exposed on the roof of a house in the neighbourhood
of Calcutta have indicated a loss of from 26 to 37 hundredths of an inch in
depth daily during the month of April. Taking this into account, along with the
fine texture of the soil, we have, I believe, arrived at an explanation of the idea
that the subsoil of Calcutta is impermeable. Deep excavations can only be
carried out in the locality during the dry season unless pumping operations are
called into play, and hence it is in the dry season only that opportunities ordin
-arily arise of seeing the subsoil. So long, however, as the air is dry enough
and the temperature high, the daily loss by evaporation will be sufficient to
do away with the amount of water constantly added by percolation, or, at
all events, to do away with enough of it to prevent conspicuous accumulations
of fluid, and when conditions alter, the appearance of water in the excavations
is liable to be credited solely to direct rainfall and access of surface drainage.
CALCUTTA;
The 15th April 1887.
On a new Genus of the Family Ustilagineæ.
BY
SURGEON-MAJOR D. D. CUNNINGHAM, M.B.,
SPECIAL ASSISTANT TO THE SANITARY COMMISSIONER WITH THE GOVERNMENT OF INDIA.
(With Plates I and II.)
The parasite forming the subject of the present paper was first observed in
the autumn of 1886 in the Botanical Garden in Calcutta. It occurred in the leaves
of Nymphœa stellata, Nymphœa lotus, and Nymphœa rubra, which, although
regarded as a mere variety by systematists, are unequivocally, so far as physiolo
-gical characters go, distinct species. It does not appear to occur either in Euryale
or Nelumbium. Whilst affecting the three Nymphœas above mentioned, it is very
much more abundant in Nymphœa stellata than in the others, and I shall there
-fore describe it in detail as occurring in that species, merely referring to any
points of variation which seem to present themselves when it affects the other
hosts.
In Nymphœa stellata it affects leaves of all ages, appearing even in quite
young ones. The first indication of its presence is the appearance of small,
circumscribed, bright yellow spots on the upper surfaces of the leaves
(Plate I, fig. 3). These spots usually occur associated in large numbers, but
occasionally perfectly isolated ones appear on otherwise healthy leaves. In
some cases they are evenly sprinkled over the entire surface, but in most cases they
tend to occur in patches or lines over limited areas of the leaf. Where very
closely set they often become confluent at the margins over comparatively large
areas. When they first appear, the alteration in the tissues of the host does not
extend to the under-surface of the leaf, which retains its beautiful deep violet
colour unaltered. After a time the centres of the yellow spots become brown and
ultimately almost black in many instances. As this change goes on, the patches
begin to appear on the lower surface as deep blue spots, which soon become
greenish centrally, and eventually decay sets in and leads to the formation
of perforations surrounded on the upper surface by yellow zones of tissue
containing the parasite.
Before proceeding to describe the characters of the parasite it is necessary
to give some account of the structure of the leaves of the host-plant. This is very
peculiar in Nymphœa stellata, and is quite distinct from that in either of the
other two species. There is an entire absence of any stratum of palisade cells,
E 2
Medical Officers of the Army of India.
29
plasm, but as time goes on the latter disappears and, the cavity becoming filled
up, the process is converted into a solid appendage of the dilatation. The latter
becomes separated from the proximal portion of its parent filament by the
formation of a septum after a great accumulation of protoplasm within it has
occurred. The young spore which has thus been differentiated is at first entire
-ly filled by a dense mass of granular matter. A gradual development of oil
globules next sets in. The globules gradually fuse with one another, forming
drops of progressively increasing size and diminishing number, and ultimately
the process ends with the development of one great globule occupying a great
part of the cavity and surrounded by a thin layer of finely granular protoplasm.
Whilst these changes have been progressing in the contents of the spores, a very
considerable thickening of the walls has also occurred and the mature spores
appear as nearly spherical cells with thick walls, a projecting beak, and oily and
protoplasmic contents.
The ripe spores are colourless or have a faint brownish tinge due to a slight
darkening of the thick epispore. The beak is always colourless. Where they
become detached they not unfrequently carry a portion of the empty parent
filament with them. They are of considerable size, measuring about 14µ , exclu
-sive of the beak, in length by 10 or 11µ in breadth. The beak is about 1·8µ in
length. As they accumulate in the substomatic spaces they frequently so fully
occupy the cavities as to form dense masses in which the individual spores are
closely pressed together and to the boundaries of the spaces (Plate II,
figs. 1, 2). When stained with eosine alone the epispore takes a bright orange
-red tint, whilst the contents become strong rose. Spiller's purple dyes the fila
-ments and spores deep violet, apparently due to staining of the cell walls. The
spores germinate in situ, and the long promycelia emerge on the surface of the
leaf, not due to any rupture of the epidermis, but by passing out through the
stomata (Plate II, fig. 15). Due to this the central darkened portions of the
patches occupied by the parasite become covered by a series of tufts of colour
-less filaments which are readily recognisable under examination with a simple
lens.
The phenomena attending germination of the spores in situ or in water
are as follows:—A gradual solution and disappearance of the great oil globule
takes place and the contents once more become evenly granular. A thick
germinal tube now emerges at some point in the lateral surfaces of the spore
(Plate II, fig. 8). This rapidly elongates, and, as it does so, the protoplasmic
contents of the spore gradually travel into it and continue to advance along its
course, leaving the lower part empty and traversed by septa. The germinal
tube thus eventually comes to consist of three or four superimposed cells.
The distal extremity next comes to show a number of short, thick branches,
with rounded extremities (Plate II, fig. 9). The protoplasm continues to
advance into these and ultimately nearly leaves the germinal tube, only a small