Chapter III: THE SOUTHERN ZONE.--Characterized by absence of Cyprinidae and (16)

Acting upon the report of this committee the Finance Bill of 1909 was framed to give effect to the principles of graduation and differentiation. The rate upon the earned portion of incomes of persons whose total income did not exceed £3000 was left unchanged, viz. 9d. in the pound up to £2000, and 1s. in the pound between £2000 and £3000. But the rate of 1s. in the pound on all unearned incomes and on the earned portion of incomes over £2000 from all sources was raised to 1s. 2d. In addition to the ordinary tax of 1s. 2d. in the pound, a super-tax of 6d. in the pound was levied on all incomes exceeding £5000 a year, the super-tax being paid upon the amount by which the incomes exceed £3000 a year. A special abatement of £10 a child for every child under the age of sixteen was allowed upon all incomes under £500 a year. No abatements or exemptions were allowed to persons not resident in the United Kingdom, except in the case of crown servants and persons residing abroad on account of their health. Certain abatements for improvements were also allowed to the owners of land or houses.

The estimated increased yield of the income tax for 1909-1910 on these
lines was £2,500,000, which excluded the abatements allowed for
improvements. The super-tax was estimated to yield a sum of £500,000,
which would be increased ultimately to £2,500,000, when all returns
and assessments were made.

The following accounts show the operation of the same system of taxation in other countries:--[2]

_Austria._--The income tax dates from 1849, but the existing tax,
which is arranged on a progressive system, came into force on the 1st
of January 1898. The tax is levied on net income, deductions from the
gross income being allowed for upkeep of business, houses and lands,
for premiums paid for insurance against injuries, for interest on
business and private debts, and for payment of taxes other than income
tax. Incomes under £50 a year are exempt, the rate of taxation at the
first stage (£52) being 0.6 of the income; at the twelfth stage (£100)
the rate is 1%, at the twenty-seventh stage (£300) it rises to 2%, at
the forty-third stage (£1000) it is 3%, and at the fifty-sixth (£2500)
it is 3½%; an income of £4000 pays 4%; from £4000 up to £8333 per
annum progression rises at £166 a step, and for every step £8, 6s. 8d.
taxation is assessed. Incomes between £8333 and £8750 pay £387, 10s.;
incomes over £8750 are taxed £20, 6s. 8d. at each successive stage of
£417, 10s. Certain persons are exempt from the tax, viz.:--(a) the
emperor; (b) members of the imperial family, as far as regards such
sums as they receive as allowances; (c) the diplomatic corps, the
consular corps who are not Austrian citizens, and the official staffs
and foreign servants of the embassies, legations and consulates; (d)
such people as are exempted by treaty or by the law of nations; (e)
people in possession of pensions from the Order of Maria Theresa, and
those who receive pensions on account of wounds or the pension
attached to the medal for bravery, are exempted as far as the pensions
are concerned; (f) officers, chaplains and men of the army and navy
have no tax levied on their pay; (g) all other military persons, and
such people as are included in the scheme of mobilization are exempted
from any tax on their pay. Special allowances are made for incomes
derived from labour, either physical or mental, as well as for a
family with several children. There are also special exemptions in
certain cases where the annual income does not exceed £4167, 10s.,
viz.--(a) special charges for educating children who may be blind,
deaf, dumb or crippled; (b) expense in maintaining poor relations; (c)
perpetual illness; (d) debts; (e) special misfortunes caused by fire
or floods; (f) being called out for military service. The tax is
assessed usually on a direct return from the individual taxpayer,
except in the cases of fixed salaries and wages, on which the tax is
collected from the employer, who either deducts it from the salary of
the employee or pays it out of his own pocket. The tax, which is
assessed on the income of the previous year, is paid direct to the
collector's office in two instalments--one on the 1st of June and the
other on the 1st of December.

_Belgium._--No income tax proper exists in Belgium, but there is a
state tax of 2% on the dividends of joint stock companies.

_Denmark._--Income tax is levied under a law of the 15th of May 1903.
Incomes under 2000 kroner pay a tax of 1.3%; under 3000 kroner, 1.4%;
under 4000 kroner, 1.5%; under 6000 kroner, 1.6%; under 8000 kroner,
1.7%; under 10,000 kroner, 1.8%; under 15,000 kroner, 1.9%; under
20,000 kroner, 2.0% and for every additional 10,000 kroner up to
100,000 kroner 1%, incomes of 100,000 kroner and upwards paying 2.5%.
Exempt from the duty are--the king, members of the royal family and
the civil list; the legations, staffs and consular officers of foreign
powers (not being Danish subjects); foreigners temporarily resident in
the country; mortgage societies, credit institutions, savings and loan
banks. The increase in capital resulting from an increase in value of
properties is not deemed income--on the other hand no deduction in
income is made if such properties decrease in value--nor are daily
payments and travelling expenses received for the transaction of
business on public service, if the person has thereby been obliged to
reside outside his own parish. Certain deductions can be made in
calculating income--such as working expenses, office expenses,
pensions and other burthens, amounts paid for direct taxation, dues to
commune and church, tithe, tenant and farming charges, heirs'
allowances and similar burthens; interest on mortgages and other
debts, and what has been spent for necessary maintenance or insurance
of the property of the taxpayer. There are also certain exemptions
with respect to companies not having an establishment in the country.

_France._--There is no income tax in France corresponding exactly to
that levied in the United Kingdom. There are certain direct taxes,
such as the taxes on buildings, _personnelle mobilière_, and doors and
windows (_impôts de répartition_)--the tax levied on income from land
and from all trades and professions (_impôts de quotité_) which bear a
certain resemblance to portions of the British income tax (see FRANCE:
_Finance_). From time to time a graduated income tax has been under
discussion in the French Chambers, the proposal being to substitute
such a tax for the existing (_personnelle mobilière_) and doors and
windows taxes, but no agreement on the matter has been reached.

_German Empire._--In Prussia the income tax is levied under a law of
the 24th of June 1891. All persons with incomes of over £150 per annum
are required to send in an annual declaration of their full income,
divided according to four main sources--(a) capital; (b) landed
property; (c) trade and industry; (d) employment bringing gain, this
latter including the salary or wages of workmen, servants and
industrial assistants, military persons and officials; also the
receipts of authors, artists, scientists, teachers and tutors.
Liability for income tax, however, begins with an income of £45, and
rises by a regular system of progression, the rate being about 3% of
the income. Thus an income of more than £45, but under £52, 10s. pays
a tax of 6s. and so on up to £475, an income over that sum but under
£525 paying a tax of 15s. Incomes over £525 rise by steps of £50 up to
£1525, for every step £1, 10s. being paid. Incomes between £1526 and
£1600 rise by steps of £75, £3 being paid for every step. Between
£1601 and £3900, the steps are £100, and the tax £4 a step; from £3901
to £5000 the steps are the same (£100), but the tax is £5 a step.
There is also a supplementary tax on property of about 1/20th% of the
assessed value. This supplementary tax is not levied on those whose
taxable property does not exceed a total value of £300, nor on those
whose annual income does not exceed £45, if the total value of their
taxable property does not exceed £1000, nor on women who have members
of their own family under age to maintain, nor on orphans under age,
nor on persons incapable of earning incomes if their taxable property
does not exceed £1000 nor their income £60. There are a number of
exemptions from the income tax, some of the more important being--(a)
the military incomes of non-commissioned officers and privates, also
of all persons on the active list of the army or navy as long as they
belong to a unit in war formation; (b) extraordinary receipts from
inheritances, presents, insurances, from the sale of real estate not
undertaken for purposes of industry or speculation, and similar
profits (all of which are reckoned as increases of capital); (c)
expenses incurred for the purpose of acquiring, assuring and
maintaining income; (d) interest on debts; (e) the regular annual
depreciation arising from wear of buildings, machines, tools, &c., in
so far as they are not included under working expenses; (f) the
contributions which taxpayers are compelled by law or agreement to pay
to invalid, accident, old age insurance, widow, orphan and pension
funds; (g) insurance premiums. Moreover, persons liable to taxation
with an income of not more than £150 may deduct from that income £2,
10s. for every member of their family under fourteen years of age, and
abatement is also allowed to persons with incomes up to £475 whose
solvency has been unfavourably affected by adverse economic
circumstances. The income tax is both levied at the source (as in the
case of companies) and assessed on a direct return by the taxpayer of
his income from all sources. Salaries are not taxed before payment.
Fixed receipts are assessed according to their amount for the taxation
year in which the assessment is made, and variable incomes on an
average of the three years immediately preceding the assessment. The
income tax and the supplementary tax are collected in the first half
of the second month of each quarter by the communities (_Gemeinden_)
who bear the whole cost.

In Saxony a graduated tax is in force on all incomes of £20 per annum
and upwards. All corporate bodies and individuals who derive their
income or any portion of it from Saxony are liable to the extent of
that income, except those serving religious, charitable or public
purposes. Incomes between £20 and £5000 are divided into 118 classes,
in which the rate rises progressively. From £500 to £5000 the classes
rise by £50, and above £5000 by £100. The rate of income tax begins at
¼%, i.e. 1s. on an income of £20. An abatement is allowed to those
whose incomes do not exceed £155 of £2, 10s. for each child between
the ages of six and fourteen years, provided such abatements do not
reduce the income by more than one class. In the case of persons with
incomes not exceeding £290 abatement (not exceeding three classes) is
allowed--(a) when the support of children or indigent relations
involves a burden of such a nature as to affect the general standard
of living; (b) on account of long-continued illness, involving heavy
expense; and, on restoration to health, temporary decrease of
wage-earning power; (c) in the case of accidents which have had the
same effect.

In Bavaria the existing system of income tax came into force on the
1st of January 1900. The rate on earned income varies according to a
scale laid down in article 5 of the law, beginning at .1% for incomes
up to £37, 10s. (1s.), being .66% (£2, 5s.) for incomes between £230
and £250; 1.03% (£4) for incomes between £350 and £375; 1.30% (£6,
16s.) for incomes between £475 and £500 and 1.38% (£10) for incomes
between £650 and £700. Incomes exceeding £700 and not exceeding £1100
pay £1 on every £50; those between £1100 and £1700, £1, 10s., on every
£50, between £1700 and £2050, £2 on every £50; between £2050 and
£2500, £2, 10s. on every £50 and beyond £2500, 3% on every £50.
Exemptions from earned income tax are similar to those already
mentioned in the case of Prussia. Special abatement in the case of
incomes not exceeding £250 from all sources is given in consideration
of education of children, protracted illness, maintenance of poor
relations, serious accidents, &c. The tax on unearned income is at the
rate of 1½% on incomes from £3, 10s. to £5; from £6 to £20, 2%; from
£21 to £35, 2½%; from £36 to £59, 3%; from £51 to £150, 3½%; from £151
to £5000, 3¾%, and over £5000, 4%. There is a differentiation in
assessment on fluctuating and fixed incomes. Fluctuating incomes (e.g.
those derived from literary, scientific or artistic work) are assessed
at the average receipts of the two past years. Fixed income is
returned at the actual amount at the time of assessment, and the
assessment for earned income, both fixed and fluctuating, takes place
every four years. Income tax is not levied at the source, but on a
direct return by the taxpayer. In the case of unearned income, where a
person's yearly unearned income does not exceed £100 and he has no
other or only an insignificant additional income, he is required to
pay only half the assessed tax. Also in the case where a total income,
earned and unearned, does not exceed £250 it may, by claiming
abatement on such grounds as the education of children, maintenance of
indigent relations, &c., be assessed at the lowest rate but one, or be
entirely exempt.

In Württemberg the General Income Tax Act came into force on the 1st
of April 1905. Article 18 provides a graduated scale of rates on
incomes from £25 upwards. Abatements are allowed for the education and
support of children, support of indigent relatives, active service in
the army and navy, protracted illness and severe accidents or
reverses. There is a supplementary tax of 2% on unearned income from
certain kinds of property, such as interest or other income derived
from invested capital, dividends, &c., from joint-stock companies and
annuities of all kinds. The income tax is not levied at the source,
but on a direct return by the ratepayers; assessments are made on the
current year, except in the case of fluctuating incomes, when they are
made on the income of the preceding year.

_Hungary._--There is no income tax in Hungary at all corresponding to
that of the United Kingdom, although proposals for such a tax have
from time to time been made.

_Italy._--Graduated income tax in Italy dates from 1864. Incomes are
classified according to their characters, and the rate of the tax
varies accordingly. In class A¹ are placed incomes derived from
interests on capital, and perpetual revenues owned by the state,
interests and premiums on communal and provincial loans, dividends of
shares issued by companies guaranteed or subsidized by the state
lottery prizes. These incomes are assessed at their integral value and
pay the full tax of 20%. In class A² are placed incomes derived from
capital alone and all perpetual revenues. The assessments on these are
reduced to 30/40ths of the actual income and taxed at a rate of 15%.
In class B are incomes derived from the co-operation of labour and
capital, i.e. those produced by industries and commerce. The
assessments of these are reduced to 20/40ths and taxed at 10%. In
class C are placed incomes derived from labour alone (private
employment) and those represented by temporary revenues or life
annuities. Assessments on these are reduced to 18/40ths and taxed at a
rate of 9%. In class D are placed incomes from salaries, pensions and
all personal allowances made by the state, the provinces and communes.
Assessments on these are reduced to 15/40ths and taxed at 7½%.
Certain abatements are allowed on small incomes in classes B, C and D.
Incomes are assessed (1) on the average of the two preceding years in
the case of private industries, professions or companies in which
liability is unlimited; (b) on the income of the current year in the
case of incomes from dividends, salaries, pensions and fixed
allowances, as well as in the case of incomes of communes, provinces
and corporations; (c) on the basis of the account closed before the
previous July of the current year in the case of incomes of limited
liability companies, banks and savings banks.

_Netherlands._--In the Netherlands there is a property tax imposed
upon income derived from capital, as well as a tax on income earned by
labour.

_Norway._--In Norway under the state income tax incomes under 1000
kroner are exempt, those between 1000 and 4000 kroner pay 2% on that
part liable to taxation; those between 4000 and 7000 kroner pay 3%;
those between 7000 and 10,000 kroner pay 4%, and those above 10,000
kroner 5%. Persons liable to taxation are divided into (a) those who
have no one to support, as companies and the like; (b) those who have
from one to three persons to support; (c) those who have from four to
six persons to support; (d) those who have seven or more persons to
support. Those who are counted as dependent upon the taxpayer are his
children, own or adopted, his parents, brothers and sisters, and other
relations and connexions by marriage who might have a reasonable claim
to his support. A certain part of the income liable to taxation is
abated by a graduated scale according to the class into which the
ratepayer falls.

_Spain._--In Spain the income tax is divided into (a) that derived
from personal exertion and (b) that derived from property. Directors,
managers and representatives of banks, companies and societies pay
10%; those employed in banks, &c., commercial houses, and those in
private employment, as well as actors, bullfighters, professional
pelota-players, acrobats, conjurers, &c., pay 5%. Those employed by
the day or those whose salary is under £45 are exempt, as are also
masters in primary schools. Income derived from property is taxed
according to the source from which the income is derived, e.g. income
from shares in public works is rated at 20%, income from shares in
ordinary companies, railways, tramways or canals at 3%, from dividends
on bank shares at 5%, from mining shares at only 2%. There is also an
industry tax, i.e. on the exercise of industrial, commercial and
professional enterprises, which tax is divided into five different
tariffs, of which I. applies to commerce (vendors), II. also to
commerce (middlemen), III. to industry (machinery), IV. to professions
and V. to licences (retail and itinerant vendors). Tariff I. is
differentiated according to the importance of the business and of the
locality in which it is carried on, the rate being fixed by a
consideration of the two combined. Tariff II. is differentiated
according to the character of the enterprise, its importance and the
importance of the locality. Tariff III. is differentiated according to
either motive power, output, method, product or locality; Tariff IV.
according to the character of the profession and the importance of the
locality; Tariff V. is also differentiated according to the locality
and the importance of the business.

_Switzerland._--The system of income tax varies in the different
cantons. Broadly speaking, these may be divided into four different
kinds: (1) a graduated property tax, in which the rate applicable to
each class of fortune is definitely fixed; (2) a proportional tax,
under which property and income are chargeable, each at a fixed rate,
while the total amount of the tax is liable to a proportionate
increase according to scale if it exceeds certain specified amounts;
(3) a system by which property and income are divided into three
classes, the rate of the tax being increased by a graduated rise,
according to the class to which the property or income belongs, and
(4) a uniform rate of tax, with progression in the amount of income
liable to taxation.

_United States._--One of the means adopted by the Federal Government
for meeting its expenses during the Civil War was the levying of an
income tax. By the Act of Congress of the 5th of August 1861 a tax of
3% was imposed on all incomes, with an exemption of $800, and was made
payable on or before the 30th of June 1862. No tax, however, was
assessed under the law. In March 1862 a new income tax bill was
introduced into the House of Representatives. This act, which was
signed on the 1st of July 1862, imposed a tax of 3% on all incomes not
over $10,000, and 5% on all incomes above that sum, with an exemption
of $600. It was also provided that dividends of banks, insurance
companies and railways should be assessed directly; but the
bond-holder was allowed to deduct the dividend so assessed from his
taxable income. In the case of government salaries, the tax was
deducted before the salaries were paid. The income tax was first
levied in 1863. The rate was changed by act of Congress in 1865, 1867
and 1870, and a joint resolution in 1864 imposed a special additional
tax of 5% for that year. The tax was finally abolished in 1872. The
total amount produced by the tax from the beginning was $376,150,209.
The constitutionality of the act was subsequently brought into
question, but was upheld by a unanimous decision of the Supreme Court
in 1880, which held that the tax was not a direct tax but an excise
tax, and that Congress had a right to impose it so long as it was made
uniform throughout the United States. On the 27th of August 1894 an
income tax act was passed as part of the Wilson Bill. By this act it
was provided that a tax of 2% on all incomes should be levied from
the 1st of January 1895 to the 1st of January 1900, with an exemption
of $4000. The legality of the tax was assailed, chiefly on the ground
that it was a direct tax, and not apportioned among the several states
in proportion to their population. On the 20th of May 1895 the Supreme
Court, by a vote of five to four, declared the tax to be
unconstitutional. Accordingly, before any federal income tax could be
imposed, there was needed an amendment of the constitution, and a
movement in this direction gradually began. In the first year of the
presidency of Mr W. H. Taft both Houses of Congress passed by the
necessary two-thirds majority a resolution to submit the proposal to
the 46 states, the wording of the amendment being "That Congress shall
have power to lay and collect taxes on incomes from whatever source
derived, without apportionment among the several States, and without
regard to any census enumeration."

_Cape Colony._--Cape Colony was the only South African colony which,
prior to the Union in 1910, had a system of income tax, which was
first imposed by an act of the 31st of May 1904. Incomes not exceeding
£1000 per annum were exempt from taxation; incomes exceeding £1000 but
not exceeding £2000 were taxed 6d. in the pound on the excess beyond
£1000; those between £2000 and £5000 were exempt for the first £1000,
paid 6d. in the pound on the next £1000 and 9d. in the pound on the
remainder; those exceeding £5000 paid 6d. in the pound on the second
£1000, 9d. in the pound on the next £3000 and 1s. in the pound on the
remainder.

_New South Wales._--Income tax in New South Wales first came into
operation on the 1st of January 1896. It is complementary with a land
tax, assessed on the unimproved value of freehold lands (with certain
exemptions and deductions). Incomes of £200 per annum and under are
exempt, and all other incomes (except those of companies) are entitled
to a reduction of £200 in their assessments. The rate of tax is 6d. in
the pound. There are certain incomes, revenues and funds which are
exempt from taxation, such as those of municipal corporations or other
local authorities, of mutual life insurance societies and of other
companies or societies not carrying on business for purposes of profit
or gain, and of educational, ecclesiastical and charitable
institutions of a public character, &c.

_New Zealand._--In New Zealand the income tax is also complementary
with a land tax. Incomes up to £300 per annum are exempt; incomes up
to £1000 per annum are taxed 6d. in the pound, with an exemption of
£300 and life insurance premiums up to £50; incomes over £1300 pay 1s.
in the pound, which is also the tax on the income of trading
companies, to whom no exemption is allowed. The income of friendly
societies, savings banks, co-operative dairy companies, public
societies not carrying on business for profit, &c., are exempt from
income tax.

_Queensland._--In Queensland income tax is levied on (a) income
derived from property such as rents, interest, income from companies,
royalties, &c., and (b) on income derived from personal exertion. On
income derived from property all incomes not exceeding £100 are
exempt; incomes between £100 and £120 pay £1 tax; those over £120 but
under £300 have £100 exempt and pay 1s. in each and every pound over
£100, while incomes over £300 pay 1s. in each and every pound. Incomes
from personal exertion pay 10s. between £100 and £125; £1 between £126
and £150; between £151 and £300 have £100 exempt and pay 6d. in each
and every pound over £100: between £301 and £500 6d. in every pound;
between £501 and £1000 6d. in every pound of the first £500 and 7d. in
every pound over £500, between £1001 and £1500 7d. in every pound of
the first £1000, and 8d. in every pound over £1000; incomes over £1500
pay 8d. in every pound; 1s. in every pound is charged on the incomes
of all companies and of all absentees.

_South Australia._--The income tax dates from 1884 and is levied on
all incomes arising, accruing in or derived from South Australia,
except municipal corporations, district councils, societies, &c., not
carrying on business for the purpose ot gain, and all friendly
societies. Where the income is derived from personal exertion the rate
of tax is 4½d. in the pound up to £800, and 7d. in the pound over
£800. For income derived from property the rate is 9d. in the pound up
to £800, and 1s. 1½d. in the pound over £800. There is an exemption of
£150 on incomes up to £400, but no exemption over that limit.

_Tasmania._--In Tasmania there is (a) an income tax proper, and (b) a
non-inquisitorial ability tax, one complementary to the other. The
income tax proper is levied on all income of any company, at the rate
of 1s. for every pound of the taxable amount; on all income of any
person, at the rate of 1s. for every pound of the taxable amount
derived from property, and on every dividend at the same rate.
Personal incomes of £400 and over are assessed at the full amount, but
an abatement of £10 for every £50 of income is allowed on incomes
below £400 down to incomes of £150, which thus have £50 deducted;
incomes between £120 and £150 have £60 deducted; incomes between £110
and £120, £70, and incomes between £100 and £110, £80. The ability tax
is paid by (a) occupiers and sub-occupiers of property and (b) by
lodgers. The amount of tax paid by occupiers or sub-occupiers is
calculated upon the assessed annual value of the property occupied,
and that of lodgers from the assessed annual value of their board and
lodging. A detailed account of both taxes will be found in House of
Commons Papers, No. 282 of 1905.

_Victoria._--In Victoria the rate of income tax is fixed annually by
act. The rate charged on income derived from property is exactly
double that charged on income derived from personal exertion, the
rate for which for 1905 was: on the first £500 or fractional part
thereof, 3d. in the pound; on the second £500 or fractional part
thereof, 4d. in the pound; on the third £500 or fractional part
thereof, 5d. in the pound; on all incomes in excess of £1500, 6d. in
the pound. All companies, except life insurance companies, were
charged 7d. in the pound on their incomes; life insurance companies
were charged 8d. in the pound.

BIBLIOGRAPHY.--The Annual Reports of the Commissioners of Inland
Revenue, the Reports of Committees and other references mentioned in
the article, as well as Dowell's _History of Taxation in England_
(1884); Dowell's _Acts relating to the Income Tax_ (6th ed., 1908),
and Robinson's _Law relating to Income Tax_ (2nd ed., 1908).

FOOTNOTES:

[1] Full statistics of the yield of income tax and other information
pertaining thereto will be found in the _Reports of the Commissioners
of His Majesty's Inland Revenue_ (published annually); those issued
in 1870 and in 1885 are especially interesting.

[2] In Appendix No. 4 to the _Report from the Select Committee on
Income Tax_ (1906), will be found a valuable list (prepared in the
Library of the London School of Economics) of references to the
graduation of the income tax and the distribution of incomes both in
the United Kingdom and in other countries.

INCORPORATION (from Lat. _incorporare_, to form into a body), in law, the embodying or formation of a legal corporation, brought about either by a general rule contained in such laws, e.g. as the Companies acts, and applicable wherever its conditions are satisfied; or by a special act of sovereign power, e.g. an incorporating statute or charter. The word is used also in the sense of uniting, e.g. a will may incorporate by reference other papers, which may be then taken as part of the will, as much as if they were set out at length in it.

INCUBATION and INCUBATORS. The subject of "incubation" (Lat. _incubare_, to brood; _in-cumbere_, to lie on), a term which, while strictly signifying the action of a hen in sitting on her eggs to hatch them, is also used in pathology for the development within the body of the germs of disease, is especially associated with the artificial means, or "incubators," devised for hatching eggs, or for analogous purposes of an artificial foster-mother nature, or for use in bacteriological laboratories.

Life is dependent, alike for its awakening and its maintenance, upon the influence of certain physical and chemical factors, among which heat and moisture may be regarded as the chief. It is therefore obvious that any method of incubation must provide for a due degree of temperature and moisture. And this degree must be one within limits, for while all organisms are plastic and can attune themselves to a greater or less range of variation in their physical environment, there is a given degree at which the processes of life in each species proceed most favourably. It is this particular degree, which differs for different species, which must be attained, if artificial incubation is to be successfully conducted. In other words, the degree of temperature and moisture within the incubation drawer must remain uniform throughout the period of incubation if the best results are to be reached. It is not easy to attain these conditions, for there are many disturbing factors. We may therefore next consider the more important of them.

The chief causes which operate to make the temperature within the incubator drawer variable are the changes of the temperature of the outer air, fluctuations in the pressure of the gas when that is used as the source of heat, or the gradual diminution of the oxidizing power of the flame and wick when an oil lamp is substituted for gas. Also, the necessary opening of the incubator drawer, either for airing or for sprinkling the eggs with water when that is necessary, tends to reduce the temperature. But there is another equally important though less obvious source of disturbance, and this resides within the organism undergoing incubation. In the case of the chick, at about the ninth or tenth days of incubation important changes are occurring. Between this period and the fourteenth day the chick becomes relatively large and bulky, and the temporary respiratory organ, the allantois, together with its veins, increases greatly in size and extent. As a consequence, the respiratory processes are enabled to proceed with greater activity, and the chemical processes of oxidation thus enhanced necessarily largely increase the amount of heat which the chick itself produces. Thus an incubator, to be successful, must be capable of automatically adjusting itself to this heightened temperature.

The drawer of an incubator is a confined space and is usually packed as closely as possible with the contained eggs. The eggs are living structures and consequently need air. This necessitates some method of direct ventilation, and this in its turn necessarily increases the evaporation of water vapour from the surface of the egg. Unless, therefore, this evaporation is checked, the eggs will be too dry at the period--from the tenth day onwards--when moisture is more than ever an important factor. There is, according to some poultry authorities, reason to believe that the sitting hen secretes some oily substance which, becoming diffused over the surface of the egg, prevents or retards evaporation from within; presumably, this oil is permeable to oxygen. In nature, with the sitting hen, and in the "Mamal" artificial incubating establishments of the Egyptians, direct air currents do not exist, owing to the large size of the chambers, and consequently incubation can be successfully achieved without any special provision for the supply of moisture.

Artificial incubation has been known to the Egyptians and the Chinese from almost time immemorial. In Egypt, at Berme on the Delta, the trade of artificial hatching is traditionally transmitted from father to son, and is consequently confined to particular families. The secrets of the process are guarded with a religious zeal, and the individuals who practise it are held under plighted word not to divulge them. It is highly probable that the process of artificial incubation as practised by the Egyptians is not so simple as it is believed to be. But as far as the structures and processes involved have been ascertained by travellers, it appears that the "Mamal" is a brick building, consisting of four large ovens, each of such a size that several men could be contained within it. These ovens are in pairs, in each pair one oven being above the other, on each side of a long passage, into which they open by a circular aperture, just large enough for a man to obtain access to each. The eggs are placed in the middle of the floor of the oven, and in the gutters round the sides the fire is lighted. The material for this latter, according to one account, consists of camels' dung and chopped hay, and according to another of horses' dung. The attainment of the right degree of heat is apparently reached wholly by the skill of the persons employed. When this has been attained, they plug the entrance hole with coarse tow. On the tenth to twelfth days they cease to light the fires.

Each "Mamal" may contain from 40,000 to 80,000 eggs. There are 386 "Mamals" in the country, which are only worked for six months of the year, and produce in that time eight broods. Many more than two-thirds of the eggs put in are successfully hatched. It is estimated that 90,000,000 eggs are annually hatched by the Bermeans.

A method of incubating that appears to have been altogether overlooked in England--or at least never to have been practised--is that carried on by the _Couveurs_ or professional hatchers in France. They make use of hen-turkeys for the purpose, and each bird can be made to sit continuously for from three to six months. The _modus operandi_ is as follows: a dark room which is kept at a constant temperature throughout the year contains a number of boxes, just large enough to accommodate a turkey. The bottom of the box is filled with some vegetable material, bracken, hay, heather, straw or cocoa-fibres. Each box is covered in with lattice-work wire, so arranged that the freedom of the sitting bird is limited and its escape prevented. Dummy eggs, made by emptying addled ones and filling with plaster of Paris, are then placed in the nest and a bird put in. At first it endeavours to escape, but after an interval of a few days it becomes quiet, and the dummy eggs being then removed, fresh ones are inserted. As soon as the chickens are hatched, they are withdrawn and fresh eggs substituted. The hen turkeys are also used successfully as foster-mothers. Each bird can adequately cover about two dozen eggs.

Incubation as an industry in Europe and America is of recent development. The growing scarcity of game birds of all kinds, coincident with the increase of population, and the introduction of the breech-loading gun, together with the marked revival of interest in fancy poultry about the year 1870, led, however, to the production of a great variety of appliances designed to render artificial incubation successful.

Previously to this, several interesting attempts had been made. As long ago as 1824, Walthew constructed an incubator designed to be used by farmers' wives with the aid of no more than ordinary household conditions. It consisted of a double-walled metal box, with several pipes opening into the walled space round the sides, bottom and top of the incubator. These pipes were connected with an ordinary kitchen boiler. Walthew, however, constructed a fire grate, with a special boiler adapted to the requirements of the incubator. Into the walled space of the incubator, steam from the kitchen boiler passed; the excess steam escaped from an aperture in the roof, and the condensed steam through one in the floor. Ventilating holes and also plugs, into which thermometers were placed, pierced the door of the incubator.

In 1827, J. H. Barlow successfully reared hens and other birds by means of steam at Drayton Green, Ealing. He constructed very large rooms and rearing houses, expending many thousands of pounds upon the work. He reared some 64,000 game birds annually. The celebrated physician Harvey, and the famous anatomist Hunter were much interested in his results.

To John Champion, Berwick-on-Tweed, in 1870, belongs, however, the credit of instituting a system which, when extended, may become the system of the future, and will rival the ancient "Mamals" in the success of the incubation and in the largeness of the numbers of eggs incubated. He used a large room through which passed two heated flues, the eggs being placed upon a table in the centre. The flues opened out into an adjoining space. The temperature of the room was adjusted by personal supervision of the fire. This system, more elaborated and refined, is now in use in some parts of America.

_Bird Incubators._

Owing to the great variety in the details of construction, it is difficult to arrange a classification of incubators which shall include them all. They may, however, be classified in one of two ways. We may either consider the method by which they are heated or the method by which their temperature is regulated.

In the former case we may divide them into "hot-air" incubators and into "hot-water" or "tank" incubators. In the latter ease we may classify them according as their thermostat or temperature-regulator is actuated by a liquid expanding with rising temperature, or by solids, usually metals.

In America incubators of the hot-air type with solid and metallic thermostats are most used, while in Europe the "tank" type, with a thermostat of expansible liquid, prevails.

For the purpose of more adequately considering the various forms which have been in use, or are still used, we shall here divide them into the "hot-air" and "hot-water" (or "tank") classes.

In the hot-air types the incubator chamber is heated by columns of hot air, while in the tank system this chamber is heated by a tank of warmed water.

(a) _Hot-Water Incubators._--In 1866 Colonel Stuart Wortley described
in _The Field_ an incubator constructed upon a novel principle, but
which appears never to have been adopted by breeders. The descriptive
article is illustrated with a sketch. Essentially the incubator
consists of four pipes which extend across the egg chamber some little
distance above the eggs. The pipes pass through holes in the side of
the incubator, which are furnished with pads, so as to render their
passage air-tight. Externally they are connected with a boiler. This
is provided with a dome through which steam escapes, and also with a
glass gauge to show the height of the water within the boiler. The
water in the boiler is kept at the boiling point, and the temperature
of the incubator is regulated by adjustment of the length of the
hot-water pipes within the egg chamber. To raise the temperature, a
greater length of the pipes is pushed into the chamber, and to reduce
it, more of their length is pulled outwards. It is claimed for this
instrument that since the temperature of boiling water at any
particular locality remains practically constant, the disadvantages
due to fluctuations in the activity of a lamp flame or the size of a
gas flame are obviated. But it has the serious disadvantage that there
is no automatic adjustment to compensate for fluctuations of
atmospheric temperature. And experiments by C. Hearson have shown that
even if the temperature of the tank or source of heat be constant,
that of the incubator drawer will nevertheless vary with fluctuations
of external temperature. Probably if the mechanical difficulties of
providing a self-regulator were overcome, it would prove an efficient
and reliable incubator. The difficulties do not seem to be
insuperable, and it appears possible that a thermostatic bar could be
so arranged as to automatically increase or decrease the length of
hot-water pipes within the incubator, and therefore the incubator
temperature.

Another early form of incubator is Brindley's, which was first in use
about 1845, and in his hands it appeared occasionally to act
successfully, but it never became generally used. The egg chamber was
lined with felt, and was placed beneath a heated air chamber, the
floor and roof of which were composed of glass. The air chamber was
heated by a number of hot-water pipes which were connected with a
copper boiler. This latter was heated by means of a lamp so
constructed as to burn steadily. The temperature of the air chamber
was regulated within certain limits by means of a balanced valve,
which could be so adjusted that it would open at any desired
temperature.

In Colonel Stuart Wortley's incubator the hot-water tubes passed
directly into the egg chamber, and in Brindley's into a chamber above
it. But in other forms of incubators in which the principle of an
external boiler connected with water tubes is adopted, the latter pass
not into the egg chamber nor into an air chamber, but open into and
from a tank of water. The floor of this tank forms the roof of the egg
chamber, so that the eggs are heated from above. This device of
warming the eggs from above was adopted in imitation of the processes
that presumably occur with the sitting hen; for it is generally
assumed that the surface of the eggs in contact with the hen is warmer
than that in contact with the damp soil or with the material of the
nest.

One of the earliest of this form of incubator is that invented by F.
Schröder, manager of the now extinct British National Poultry Company.
In this incubator the form is circular, and there are four egg
drawers, so that each one occupied the quadrant of a circle, and the
inner corner of each drawer meets in the middle of the incubator. From
the centre of the incubator a vertical chimney passes upwards and
opens out from the inner corners of the four egg drawers. This chimney
acts as a ventilator to the incubating chambers. These latter are open
above, but their floors are made of perforated zinc, and when in use
they are partially filled with chaff or similar material. Under them
is a tank containing cold water and common to all four drawers; the
slight vapour rising from the surface of the water diffuses through
the egg drawers and thus insures a sufficient degree of humidity to
the air within. Above the egg drawers is a circular tank containing
warm water. The floor of this tank constitutes the roof of the egg
drawers, while the roof forms the floor of a circular chamber above
it, the side wall of which is composed of perforated zinc. This upper
chamber is used to dry the chicks when they are just hatched and to
rear them until they are strong enough for removal. It is partially
filled with sand, which serves the double purpose of retaining the
heat in the warm-water tank beneath and of forming a bed for the
chicks. The water in the warm-water tank is heated by means of a
boiler which is external to the incubator, and in communication with
the tank by means of an inlet and an outlet pipe. There is no valve to
regulate the temperature, and the latter is measured by means of a
thermometer, the bulb of which is situated not in the incubator
drawers, but in the warm-water tank. This is a wrong position for the
thermometer, since it is now known that the temperature of the water
tank may be different by several degrees to that of the egg drawer;
for with a fall of external temperature that of the latter necessarily
tends to fall more rapidly than the former. But, none the less, in
skilful hands this incubator gave good results.

T. Christy's incubator, which we shall describe next, has passed
through several forms. We shall consider the most recent one (1894).
The incubator (fig. 1) is double walled, and the space between the two
walls is packed with a non-conducting material. In the upper part of
the incubator there is a water tank (T) divided by a horizontal
partition into two chambers, communicating with each other at the
left-hand side. Below the tank is the incubation drawer (E), which
contains the eggs and also a temperature regulator or thermostat (R).
The tank is traversed by a ventilating shaft (V), and inserted into
this is a smaller sliding tube passing up to it from a hole in the
bottom of the incubator drawer. The floor of the incubator drawer is
perforated, and beneath it is an enclosed air space which opens into
the sliding air shaft just described. Fresh air is let into the
incubator drawer from a few apertures (I) at its top. The ventilating
shaft (V) is closed externally by a cap (C), which can be raised from
or lowered down upon its orifice by the horizontal arm (H) working
upon pivot joints at (P). This arm is operated by the thermostat (R),
through the agency of a vertical rod. The water in the tank is heated
by an external boiler (B) through two pipes, one of which (T) serves
as an inlet, and the other (L) as an outlet channel from the tank.
These two pipes do not open directly into the tank, but into an outer
vessel (O) communicating with it. Communication between this vessel
and the tank may be made or broken by means of a sliding valve (S),
which is pierced by an aperture that corresponds in position with the
upper of the two in the wall of the tank when the valve is up. When
this valve is in its upper position, the tank (T) communicates with
the outer vessel (O) by two apertures (A and A´), the top one being
the inlet and the lower one the outlet. These coincide in position
with the tubes from the boiler. This latter (B) is a conical vessel
containing two spaces. The heated water is contained in the outer of
these spaces, while the central space is an air shaft heated by a lamp
flame. This particular form of the boiler results in the water at its
top part being more heated than that in its lower. As a consequence of
this, a continual circulation of water through the tank ensues. The
more heated water, being specifically lighter, passes into the outer
vessel, where it remains among the higher strata, and therefore enters
the tank through the upper aperture. In passing along the upper
division of the tank it becomes slightly cooled and sinks therefore
into the lower compartment, passes along it, and out through the
aperture A´. Hence it passes into the lower portion of the boiler,
where it becomes warmed and specifically lighter; in consequence it
becomes pushed upwards in the boiler by the cooler and heavier water
coming in behind and below it.

Should the temperature in the incubator drawer rise, the bimetallic
thermostat (R) opens out its coil and pulls down the vertical rod.
This simultaneously effects two things: it raises the cap (C) over the
ventilating shaft and allows of a more rapid flow of fresh air through
the incubator drawer, and it also lowers the slide-valve (S) so that
the tank becomes cut off from communication with the outer vessel (O)
and therefore with the boiler. The temperature thereupon begins to
fall and the thermostat, coiling closer, raises the vertical rod,
closes the ventilating shaft, and once more places the tank in
communication with the boiler.

The structure of the thermostat is given below.

The Chantry Incubator (Sheffield) is also an incubator with a
hot-water tank, the circulation of which is maintained by an outside
boiler. Its temperature is regulated by a metal regulator.

In Schröder's and Christy's incubators the hot-water pipes from the
boiler simply entered the warm-water tank but did not traverse it. In
the two incubators to be next described the hot-water pipes are made
to pass through the water in the tank, and are so arranged as to
minimize the possibility that the outside of the tank may become
colder than the centre. Both of them are also fitted with an ingenious
though slightly complex valve for maintaining an approximately
constant temperature.

Halsted's incubator was the earliest of this type. Since his original
form was constructed he has designed an improved one, and it is this
latter which will be described.