owing to its proximity to the great volcano, the Misti, 19,000 ft.
in height above sea-level, the city being 7000 ft. above sea-level.
The general construction of the houses is peculiar. A light coloured
volcanic stone is largely used; this, when quarried, is easily
shaped, and it hardens gradually. The roofs are for the most part
strong arches, a very good mortar being used. In the earthquake of
1868, it was not so much those arches which failed as the walls, and
the spandrels between the arches at front and rear. In some parts
of the city, arches extending in one direction stood, while those
at right angles to these were thrown down. Since 1868, a good many
corrugated iron roofs have been introduced; but they are not suitable
to the climate, and are not durable.
Earnshaw, from an experience of 25 years in Manila, where the
earthquakes are sometimes very severe, comes to the conclusion to
build as strongly as possible, and chiefly in wood, tied and bolted
together as in a ship, stone and brickwork only being used in the
lower story and in the foundations, and especial attention ought to
be paid to the quality of the lime and mortar used in construction.
Many materials have been used as roofing, such as the heavy tiles
made in the country and others imported there. When, in 1880, fully
60 per cent. of the buildings in Manila had been ruined, an order
was issued by the municipal authorities to use corrugated iron or
zinc sheeting for that purpose. A diversity of opinion existed as to
which was the best and most suitable, for not only had earthquakes to
be guarded against, but intense heat and disastrous typhoons. With
reference to the latter, in 1881, sheets of iron were flying about in
the air like paper. He thinks, therefore, that a light, strong tile
roofing is preferable to any other.
Prof. C. Clericetti, of Milan, and W. H. Thelwall relate that after
the earthquake in the island of Ischia in 1883, which was of a most
destructive character, and caused an enormous amount of damage in
the island, 2000 persons having lost their lives, and many more
being injured, a commission was appointed by the Italian Government
to obtain information, and to frame rules for the rebuilding of the
structures. It was ascertained that, speaking generally, buildings
founded on hard, solid lava had withstood the shock successfully,
whilst those founded upon looser or lighter materials, such as
tufa or clay, had suffered very much, and therefore in regard to
the re-erection of buildings it was pointed out that the first
thing to do was to select eligible sites, and to build, wherever
possible, upon lava; and, where that was not possible, to dig down
to comparatively solid ground, and then fill in a heavy platform
of masonry or concrete, 3 ft. or 4 ft. thick, extending over the
whole area of the building, and projecting 3 ft. or 4 ft. beyond.
The building of any kind of vaulting above ground was forbidden.
Light arches were only to be allowed over window’s and openings of
that kind. The heavy flat roofs formerly used to a large extent
were condemned. The commission recommended that buildings should
be chiefly constructed with an iron or wooden framework, carefully
put together, joined by diagonal ties, horizontally and vertically,
with spaces between the framework filled in with masonry of a light
character. The joists and the roof trusses were to be firmly
connected together. In plan, buildings should be square, and where
the direction of the last shock could be traced, one diagonal should
be placed in this direction. Not more than two stories above ground
were to be allowed, and there might be one under ground, but it must
be of very moderate height. In no case was the height from the lowest
point of the ground to the top of the walls to exceed 31 ft. Openings
for doors and windows were to be vertically over each other, the
jambs being not less than 5 ft. from the corner of the building. No
openings for flues were allowed in the thickness of the walls, and no
projections from the face of a building, except light balconies of
wood or iron. If solidly built structures, and particularly if there
was only one story above ground, the roofs might be covered with
tiles; but these must be light, and fastened with nails or hooks, so
as not to be displaced even by violent shocks.
=Water Supply and Purification.=--The supply of water to both town
and country houses has been dealt with at length by Eassie and Rogers
Field in essays written for the Health Exhibition Handbooks, and the
following information is mainly condensed and adapted from their
papers.
The conditions of supply in the two cases differ in being from a
general and public source in the one and from a special and private
source in the other. In each case, the consumer has to control the
purity and application of the supply after its delivery into the
dwelling; and in the second case he is further responsible for the
character and quantity of the supply before delivery. The second
case, therefore, in a great measure covers the first, and demands
extended treatment.
_Amount required._--The first consideration is the quantity of water
required. The supply to towns from waterworks is usually expressed in
“gallons per head of population per diem,” and varies exceedingly,
much of the variation being due to waste. This is especially the case
in towns where the supply is intermittent. In several towns having
a constant supply, steps have been taken systematically to measure
the water supplied to different streets and districts, and it has
been found that, without restricting the supply in any way, the
consumption of water has been immensely reduced, simply by sending
inspectors to make a house-to-house visitation and search out and
repair leaky pipes and defective taps and ball-cocks. It is by no
means an unusual thing for the consumption to be reduced one-half by
inspections of this kind, showing that at least one-half of the water
which was previously supplied to the houses was simply wasted through
leaky fittings.
Many people are inclined to think that waste of this kind is not a
bad thing, as it must help to keep the drains flushed. Field points
out that this is quite a mistake. A small dribble of water from a
leaky pipe or a leaky tap, though it will waste a great deal of water
in the course of 24 hours, is perfectly useless for flushing the
drains. What is wanted for this is the sudden discharge of a large
quantity of water. The dribble of water from leaky pipes and taps
does no good in any way, but simply wastes what might be usefully
employed, and in many cases causes a supply to run short which would
otherwise be ample for all legitimate uses. Another point that it is
difficult to realise is the large quantity of water which will run
to waste through what is apparently a very small leak. The quantity
leaking looks so small in comparison with the quantity running
when a tap is open, that one is inclined to think it perfectly
insignificant, forgetting that the leakage goes on continuously night
and day, whereas the tap is only open for a few minutes. In country
houses, where it is often difficult to obtain a sufficient supply
of water, it is particularly important to bear in mind the serious
influence that leaky pipes and taps have on the consumption, and
never to allow such leakage to go on for any length of time.
While useless waste should be prevented, it is most important that
the legitimate use of water should be encouraged in every way. As
Dr. Richardson has well pointed out, absolute cleanliness, properly
understood, is the beginning and the end of sanitary design, and
thorough cleanliness, of course, can never be obtained without an
ample water supply. Not only should there be sufficient water for
baths, lavatories, and washing of all kinds, but there should be a
liberal allowance for flushing water-closets and all other sanitary
appliances. Taking these sanitary considerations into account, as
well as giving due weight to the observations which have been made by
engineers and others on the quantity of water actually used in houses
under different circumstances, it may be assumed that, if waste is
efficiently prevented, a supply of 20-25 gallons per head per diem is
sufficient in ordinary cases for houses with baths and water-closets.
If horses are kept, a separate allowance should be made for them,
and for stable purposes (a useful approximate rule being to reckon
a horse as a man); and if water is used for watering gardens or
ornamental purposes, this must also be reckoned separately. If
earth-closets are adopted instead of water-closets, less water will
be required, and 15-20 gallons per head per diem will be sufficient.
In cottages with earth or other dry closets, the quantity of water
required will be still less: 10 gallons per head will be an ample
supply, and even 5-6 gallons may do in cases where it is absolutely
necessary to limit the quantity used.
_Sources of Supply._--Water for country houses is, in the vast
majority of cases, derived from springs or wells. Rain-water
collected from roofs is very frequently used as an auxiliary, and
occasionally as the main supply. There are instances in which the
supply is taken from streams or rivers, and even some in which water
running off the surface of the ground is collected in “impounding
reservoirs” (a mode often adopted for the water supply of towns); but
these cases are exceptional, and attention will here be confined to
springs, wells, and roof-water.
The real source of all fresh water supply is rain. Springs and wells
form no exception to this rule, though in their case the connection
with the rainfall is not so clear at first sight as it is in the
case of streams and open watercourses, because the passages by
which the rain reaches springs or wells are not visible, and heavy
rainfalls often have no apparent effect on their yield. In various
parts of the country occur curious intermittent springs (locally
called “bournes”), which burst out in some years and not in others,
and the connection between which and the rainfall is still more
obscure. Rain-water, before it issues from the ground as springs,
accumulates in the porous strata beneath, and forms, as it were,
large underground reservoirs; it is from these reservoirs that wells,
sunk into the porous strata, derive their supply.
The amount of rain varies enormously in different parts of the
world, some districts being either absolutely rainless, or having
only a very few inches of rain in the year, whereas others have some
hundreds of inches in the year. Even in England itself there is
considerable variation. The average rainfall for the whole country
is about 30 inches a year, but the amount in different parts of the
country varies from about 20 inches to nearly 200 inches a year. The
eastern side of England, as Field remarks, has much less rain than
the western side, and, roughly speaking, if a line be drawn from
Portsmouth to Newcastle-on-Tyne, it will divide the country into a
dry portion and a wet portion. The portion of the country on the east
of this imaginary line will (with the exception of the south coast,
which is wetter) have only 25 inches of rain or less, and the portion
on the west of the line will have from 30 to 50 inches, with much
larger amount in the Cumberland and Welsh mountains, and at Dartmoor.
The rainfall of the wettest year is about double that of the driest
year. This gives a very useful rule for roughly ascertaining the
extreme rainfalls, which are really more useful for the purpose of
water supply than the rainfall for an average year. The fall in the
driest year may be assumed to be one-third less than the average, and
for the wettest one-third more. Thus, with an average rainfall of 30
inches, the fall of the driest year would be 20 inches, and that of
the wettest year 40 inches.
A portion only of the total rain which falls is available for water
supply, as there is always more or less loss. In the case of rain
falling on roofs, the loss is comparatively small, but in the case
of rain falling on the surface of the earth the loss is considerable.
The latter is disposed of in three different ways: part of it runs
directly into open watercourses and streams, part is taken up by
vegetation or lost by evaporation, and part percolates through the
surface ground and accumulates in the water-bearing strata which feed
the springs and wells.
From observations made on the amount of percolation in different
cases, it has been found that the amount of percolation does not
depend so much on the amount of rain as on the conditions under
which it falls. By far the greater portion of the percolation takes
place in winter and comparatively little in summer, the reason
being that in winter the ground is wet, evaporation is small, and
vegetation is inactive, so that a large proportion of the rain sinks
into the ground; whereas in summer the reverse is the case, so that
most of the rain is taken up before it can percolate. So great is
the difference between summer and winter as regards percolation,
that one may generally leave the summer rainfall altogether out
of consideration, and assume that, in this country, it depends on
the amount of rain which falls during the six months from October
to March, whether the underground store of water will be fully
replenished or not.
The height of the accumulated underground water is indicated by
the level at which water stands in wells: and it is found that
this height varies considerably, the variations usually following
a regular course: the water is generally lowest in October and
November, it then rises till it reaches its highest point in February
or March, and after this it falls slowly till the following autumn.
A condition to be studied in selecting a spring as a source of water
supply is its “seasonal” variation. As Field points out, a spring
which will give an ample quantity of water in the winter may give an
insufficient quantity in the autumn, so that the measurement of a
spring in winter should never be depended on for determining whether
it will do as a source of water supply. The only safe way is to wait
till the autumn yield has been ascertained; even then an allowance
must be made for the previous winter, if it has been a very wet one,
the yield of the spring becoming abnormally high.
Wells may be either shallow or deep. The latter are always
preferable, but sometimes the former must be relied on. The great and
serious danger in connection with shallow wells is their liability to
pollution from cesspools and drains, whose liquid contents (fully as
poisonous as the solid) filter through the surrounding soil and go
to swell the volume of water in the well, especially if, as nearly
always happens, the cesspool is much shallower than the well.
In country villages, frequently the cesspools and wells are so
intermixed that the entire bed of water is polluted, and hence
all the wells are unsafe. But in isolated houses, if the well and
cesspool are some distance apart, pollution of the well will depend
chiefly on the direction of the movement of the underground water.
If this movement is from the cesspool towards the well, the polluted
water will flow towards the well; if the movement is in the contrary
direction, the polluted water will flow away from the well. Hence
Field’s caution, that before sinking a shallow well where sources of
contamination are in the neighbourhood, the direction of the flow of
the underground water must first be carefully ascertained, bearing in
mind that it is not safe to assume that this flow is in the direction
of the fall of the land, though it very frequently is so: if there is
the slightest doubt, levels must be taken of the underground water
in different places, and the source of contamination be accurately
localised. Contamination from surface soakage can frequently be
prevented by raising the top of the well above the adjoining ground,
and paving the surface round the well with a slope so that the
rain-water runs away from it. Norton Tube wells, which consist of an
iron tube driven into the ground and surmounted by a pump, are useful
for excluding surface pollution. If the pollution is sufficient
to contaminate the subsoil and reach the underground water, no
precautions that can be taken in constructing the well will keep the
pollution out.
Generally, deep wells are safer from contamination than shallow
wells, but may still, under certain circumstances, be polluted.
On the question whether a well which has been-polluted by a cesspool
will become fit for use after the cesspool has been removed, no
rule can be laid down. If the removal of the sources of pollution
has been thorough, the well will frequently recover its purity; but
under other circumstances the well may remain impure. As to the least
distance between wells and cesspools compatible with safety, while
the Local Government Board of London is content with 20-30 yards, Dr.
Frankland insists on at least 200 yards. It would be more rational to
forbid cesspools of all kinds; at the same time, possible leakages
from drains, through injury or otherwise, must not be omitted from
the estimate of risk of pollution. Again, the effect of increased
demand upon the contents of the well at once extends the danger,
because as the water in the well is lowered so is the area from which
the well draws its supply increased, the ratio varying from 20 to 100
times the depression. Where a whole day’s supply is pumped at once
into an elevated tank, the maximum figure will be reached.
Those who intend sinking wells are advised first to read a little
book by Ernest Spon, on the ‘Present Practice of Sinking and Boring
Wells,’ 2nd edition, 1885.
Rain-water collected from roofs forms a valuable auxiliary supply too
often disregarded. In towns it is rarely pure enough for domestic
use, but in country districts it is generally wholesome.
A country resident thus describes the manner in which he utilises
rain-water, falling upon an ordinary tin roof, covered with some sort
of metallic paint, said to contain no lead, and flowing into a large
cemented brick cistern, whence it is pumped into the kitchen. The
cistern differs from the usual construction in this manner: across
the bottom, about 3 ft. nearer one side than the other, is excavated
a trough or ditch about 2 ft. wide and 2 ft. deep; along the centre
of this depression is built a brick wall from the bottom up to the
top of the cistern, and having a few openings left through it at the
very bottom. The whole cistern, bottom, sides, and canal included,
is cemented as usual, excepting the division wall. Upon each side of
the wall, at its base, 6-12 in. of charcoal is laid, and covered with
well-washed stones to a further height of 6 in., merely to keep the
charcoal from floating. The rain-water running from the roof into the
larger division of the cistern, passes through the stone covering,
the charcoal, the wall, the charcoal upon the other side, lastly, the
stones, and is now ready for the pump placed in this smaller part. It
is much better that the water at first pass into the larger division,
as the filtration will be slower, and the cistern not so likely to
overflow under a very heavy rainfall. He has used this cistern for
many years, and was troubled only once, when some toads made their
entrance at the top, which was just at the surface of the ground,
soon making their presence known by a decided change in the flavour
of the water.
If the house chances to be in a dusty situation, several plans will
suggest themselves whereby a few gallons at the first of each rain
may be prevented from entering the cistern. Should the house be
small, and therefore the supply of water from its roof be limited, do
not lessen the size of the cistern, but rather increase it, for with
one of less capacity some of the supply must occasionally be allowed
to go to waste during a wet time, and you will suffer in a drought,
whereas a cistern that never overflows is the more to be relied upon
in a long season without rain.
Rainfall varies exceedingly in different places, and even in the same
situation it is impossible to foretell the amount to be expected
during any short period of time, but the most careful observations
show that about 4 ft. in depth descends at New York and vicinity
every year, or nearly 1 in. a week. If this amount were to be
furnished uniformly every week, the size of a cistern need only be
sufficient to contain one week’s supply, but we often have periods
of 4 weeks without receiving the average of one, and we must build
accordingly.
The weekly average of 1 in. equals 1 cub. ft. upon every 12 ft. of
surface, or 3630 cub. ft. upon an acre, weighing about 113 tons.
Upon a roof 40 ft. by 40 ft., 1600 sq. ft., it would be 133 cub.
ft., 1037 gal., or about 26 barrels of 40 gal. each. A cistern 8 ft.
across and 10 ft. deep would contain 502 cub. ft.; and one of 10
ft. across and 10 ft. deep, 785 cub. ft., or 6120 gal.--about the
average fall upon a roof of the above size for 6 weeks; while the
smaller cistern would hold 3900 gal., or a little less than 4 weeks’
rainfall. The weekly supply of 1037 gal. is equal to 148 gal. per
day, or nearly 15 gal. to each individual of a family of 10. This is
certainly enough, and more than enough, if used as it should be; but
where water is plentiful it is wasted, and in our capricious climate,
whether we depend upon wells or cisterns, it is wise to waste no
water at all, at least during the warm summer months, and lay by
not for a wet but a dry day. For this country, Field estimates 2-3
gallons of tank capacity for every square foot of roof area.
[Illustration: 3. Rain-water Tank.]
In Fig. 3 _a b c d_ show the excavation that must be made for
the cistern, and supposing the diagram to exhibit, as it does, a
section of the cistern, the receptacle for the water will be, when
finished, taking the relative proportions of the different parts into
consideration, just about 9 ft. wide and 4½ ft. deep. Of course,
the excavation must be made greater in breadth and depth than the
dimensions given, to allow for the surrounding walls and the bottom.
The walls may be of brick, cemented within, and backed with concrete
or puddled clay without, or of monolithic concrete; but the bottom,
in any case, should be made of concrete. The trench _e f g h_ running
across the bottom of the cistern is 2 ft. broad and 2 ft. deep. In
the middle of this opening is built up a 9 in. brick wall, or a
party-wall of concrete, _i k_. Along the bottom of the wall openings
_l_ are left at intervals. The party-wall divides the entire space
into the larger outer cistern _m_, and the smaller inner cistern _n_.
Supposing the breadth from _e_ to _f_ to be 2 ft., and the wall 9
in., spaces of 7½ in. will be left on each side of the wall. These
are filled to ¾ the height, or for 18 in., with lumps of charcoal,
smooth pebbles, 1-3 in. in diameter, being laid along the top of the
charcoal till the trench is filled up. The cistern is so constructed
that the water from the roof enters _m_; it passes downwards through
the stones and charcoal, as shown by the arrow at _f_, goes through
the opening and forces its way upwards in the direction of the arrow
at _e_ into the cistern _n_, in which it rises to the level of the
water in _m_, to be drawn thence for use by a small pump.
Various modifications of this form of tank-filter will suggest
themselves to readers possessing any mechanical genius. The great
point is to prevent contamination from the soil by using good
material and making sound work. Further, the overflow pipe of the
tank must not communicate with any drain or sewer.
[Illustration: 4. Rain-water Separator.]