The Rev. Professor Haughton, in his work ent.i.tled 'A New Theory of Manual Labour,' has drawn up a table (which we append) of the amount of force expended during various kinds of work. It represents the number of tons lifted one foot per diem:--

------------------------------------------------------------------------ Labouring Force of Man.

----------------------------------+-------------------------+----------- Kind of Work.

Amount of Work.

Authority.

----------------------------------+-------------------------+----------- Pile-driving

312 tons lifted 1 foot.

Coulomb.

Pile-driving

352 " "

Lamaude.

Turning a winch

374 " "

Coulomb.

Porters carrying goods,

325 " "

"

and returning unladen

Pedlars always loaded

303 " "

"

Porters carrying wood up a stair,

381 " "

"

and returning unloaded

Paviours at work

352 " "

Haughton.

Military prisoners

310 " "

"

at shot drill (3 hours),

and oak.u.m-picking and drill

Shot drill alone (3 hours)

1607 " "

"

Professor Haughton has devised a formula by means of which a certain amount of walking exercise may be made to represent its equivalent in manual labour. He points out that walking on a level surface is equivalent to raising one twentieth part of the weight of the body through the distance walked.

When ascending any height, the whole weight of the body is, of course, raised through the ascent. The formula is--

(W + W_{l}) D --------------- 20 2240

where W is the weight of the person; W_{l} the weight carried (if any); D the distance walked in feet; 20 the co-efficient of traction; and 2240 the number of pounds in a ton. The result is the number of tons raised one foot. To get the distance in feet 5280 must be multiplied by the number of miles walked.

Supposing a man to weigh 150 lbs. with his clothes, by the employment of the above formula we should arrive at the following results:--

+----------------------+------------+

Work done in

Kind of Exercise.

tons lifted

1 foot.

+----------------------+------------+

Walking 1 mile

1767

+----------------------+------------+

Walking 2 miles

3534

+----------------------+------------+

Walking 10 miles

1767

+----------------------+------------+

Walking 20 miles

3534

+----------------------+------------+

Walking 1 mile

and carrying 60 lbs.

2475

+----------------------+------------+

Walking 2 miles

and carrying 60 lbs.

495

+----------------------+------------+

Walking 10 miles

and carrying 60 lbs.

2475

+----------------------+------------+

Walking 20 miles

and carrying 60 lbs.

495

+----------------------+------------+

From the above data something like a rough approximation may be formed of the daily amount of exercise requisite for a healthy male adult.

Since 500 tons lifted a foot is extremely hard work, the number of miles corresponding to this extreme amount of labour would, if persevered in, be objectionable.

Dr Parkes, regarding 300 tons lifted a foot as an average day's work for a healthy man, thinks that walking exercise equivalent to half that amount should be taken daily. This, or a 150 tons, represents a nine miles'

walk. He, however, qualifies the suggestion by adding "that, as there is much exertion taken in the ordinary business of life, this amount may be in many cases reduced;" and concludes by saying, "It is not possible to lay down rules to meet all cases, but probably every man with the above facts before him could fix the amount necessary for himself with tolerable accuracy."

For muscular exercise to be safe and efficient, it must be taken under certain conditions and precautions. We have noticed the evil effects of immoderate bodily exertion on the heart. The lungs are no less seriously affected by an excessive indulgence in it, which shows itself in spitting of blood and in congestion of the pulmonary vessels. Congestion of the lungs brought on by overtaxed bodily strength very frequently causes the death of horses in the hunting field.

These facts, therefore, not only point to the importance of avoiding undue or extreme exertion,[293] but also to the necessity of ensuring the full and uncramped play of the respiratory organs during exercise, and the consequent removal of any impediment in the way of tight clothing that in any manner interferes with their freedom of exercise. Laboured respiration and sighing are indications of pulmonary congestion, and counsel temporary rest and abstention from exercise.

[Footnote 293: "There must be proper intervals of rest, or the store of oxygen, and of the material in the muscles which is to be metamorphosed during contraction, cannot take place."

--PARKES.]

The great augmentation in the excretion of carbon which leaves the lungs in the form of carbonic anhydride during exercise has been already referred to. As this carbon is derived from the food, it follows that in the intervals of exercise an increase of carbonaceous diet is necessary.

For this purpose physiologists prefer the fatty to the amylaceous varieties of diet. It has been already stated why at the same time the nitrogenous food must be increased during periods of great exertion. There seems little doubt that water is the best drink that can be taken during moderate as well as great exercise.... It is best taken in small quant.i.ties and frequently. Spirits are decidedly prejudicial, and indispose to bodily exertion. They are hurtful because they lessen the exhalation of carbonic anhydride from the lungs. Trainers never allow them, and but very little wine or beer.

The thirst that not unfrequently accompanies exercise is due to the great escape of water from the skin which has been already alluded to. This liberation of moisture, being also accompanied, as already explained, by a large excretion of the chlorides and, perhaps, by other salts. Dr Parkes advises the use of an additional supply of chloride of sodium to the diet of those taking much exercise; he suggests that probably pota.s.sium chloride and phosphate might be added with advantage.

The evaporation from the skin has the effect of reducing the bodily temperature and rendering it equable. This temperature, however, falls very rapidly after exertion is over; and hence at this time it is always advisable to guard against the chance of a chill by covering the body over. Flannel forms the best protection. Keeping the skin clean by daily ablution greatly aids in the escape of fluid during exercise.

The large amount of carbonic anhydride given off by the lungs during bodily exercise explains the advantages of open air exercise, and why walking in the fresh air produces such excellent effects in some forms of dyspepsia. This increased exhalation of carbonic anhydride also points to the importance of thorough ventilation when indoor exercise is taken, particularly by large bodies of men or women, as in riding schools and on the treadmill. The mortality amongst miners, whose labour is performed in confined and ill-ventilated s.p.a.ces is very great. According to Mr Simon, with the exception of those who work in the well-ventilated mines of Durham and Northumberland, the 300,000 miners in England break down prematurely from bronchitis and pneumonia, caused by the atmosphere in which they are compelled to work.

=EXPAN'SION.= All substances, solid, liquid, and gaseous, when chemical change does not take place, expand by heat, and contract by cold. In some of them this property occurs in a greater degree than in others, but is constant for the same substance under the same circ.u.mstances. The chemist avails himself of this property in the construction of his thermometer; the wheelwright, in fixing on the tire of his wheels; the engineer, in restoring to the perpendicular the leaning walls of buildings, &c.

This expansion by heat is of great importance in the manufactures, as allowance has to be made of it in every purpose where metals are employed.

The following is a list of the expansion of the chief metals, &c., when heated from 32 to 212 Fahr., or from 0 to 100 Cent.:--

_Substance._ _Expansion._ In bulk. In length.

Gla.s.s 1 in 384 1 in 1150 Platinum 1 in 377 1 in 1311 Steel 1 in 309 1 in 926 Iron 1 in 282 1 in 846 Gold 1 in 227 1 in 682 Copper 1 in 194 1 in 582 Bra.s.s 1 in 179 1 in 536 Silver 1 in 175 1 in 524 Tin 1 in 172 1 in 516 Lead 1 in 117 1 in 351 Zinc 1 in 113 1 in 340

Of the liquids, they expand as follows, when heated from 0 to 100 Cent., or from 32 to 212 Fahr.:--

Mercury 1 in 55 in bulk.

Water 1 in 21 in bulk.

Gases practically all expand alike; that is to say, for every degree Fahrenheit a gas expands 1/491 of its bulk at 32, and for every degree Centigrade 1/273 of their volume at 0C.

An example will show the importance of this. Suppose an iron bar, connecting two sides of a building, and of a length of about 85 feet. The increase in length by heat of this bar would make it 1 inch longer in summer than in winter; and it would, if no allowance be made, pull or thrust the walls to this extent each year.

=EXPEC'TORANTS.= _Syn._ EXPECTORANTIA, L. Medicines that promote the secretion of the trachial and bronchial mucus. According to Dr Good, true expectorants are "those medicines which rather promote the separation of the viscid phlegm with which the bronchiae are loaded, than simply inviscate and dilute it; though these are also treated as expectorants by many writers." Ammoniac.u.m, antimonials, a.s.saftida, the balsams of Peru and tolu, benzoic acid, benzoin; the fumes of vinegar, tar, and several of the volatile oils; garlic, ipecacuanha, the oleo-resins, squills, tartarised antimony, and the smoke of tobacco and stramonium, are among the princ.i.p.al substances commonly called expectorants. Tartarised antimony, squills, chlorine, and ammoniacal gases, have also been used (diluted) to provoke the coughing and favour the expulsion of foreign bodies from the air-pa.s.sages; and also to favour the expectoration of mucus, pus, and membranous concretions, when the local irritation is not sufficiently great. (Schwilgue.) Expectorants are commonly employed in pulmonary complaints and affections of the air tubes, attended by a vitiated state of the mucus, or an imperfect performance of the natural functions of the secretory vessels. "Of all cla.s.ses of the materia medica, none are more uncertain in their action than expectorants." (Pereira.) The act of ejecting matter from the chest is called EXPECTORATION.

=EXPER'IMENTS= are acts or operations intended to develop some unknown fact, principle, or effect; or to establish or demonstrate it, when discovered. Similar operations, performed merely for amus.e.m.e.nt, are also often, though incorrectly, called by this name. In rational experiments these two objects are combined. To experimental research is due the present high state of advancement and usefulness of the various sciences most intimately connected with our happiness and well-being. The danger of taking things for granted has been thus pleasantly and instructively pointed out by Archbishop Whately:--"It was objected to the system of Copernicus, when first brought forward, that if the earth turned on its axis, as he represented, a stone dropped from the summit of a tower would not fall at the foot of it, but at a great distance to the west; in the same manner as a stone dropped from the masthead of a ship in full sail does not fall at the foot of the mast, but towards the stern. To this it was answered, that a stone, being a part of the earth, obeys the same laws, and moves with it; whereas it is no part of the ship, of which, consequently, its motion is independent. The solution was admitted by some, but opposed by others; and the controversy went on with spirit; nor was it till one hundred years after the death of Copernicus that, the experiment being tried, it was ascertained that the stone, thus dropped from the head of the mast, _does_ fall at the foot of it."

=EXPORTATION.= (EXPORTATION ON DRAWBACK.) By law, a certain allowance, or drawback of duty, is payable on certain articles, when exported from any part of the United Kingdom, either as merchandise or ship stores. Thus:--

SUGAR, refined in the United Kingdom, from 4_s._ to 6_s._ per cwt., according to quality.

TOBACCO, manufactured in the United Kingdom, 3_s._ 3_d._ per lb. The full drawback is only allowed on normal tobacco, which contains 13 per cent. of moisture. If the moisture exceeds 13 per cent., a proportionate reduction is made in the drawback; if it is found less than 13 per cent., a proportionate increase is granted.

SNUFF is ent.i.tled to drawback at 3_s._ 3_d._ per lb., subject, however, to an increase if the moisture is less than 13 per cent., and the inorganic matter not over 18 per cent., and to a decrease if the moisture in organic matter exceeds these per-centages.

BEER. The amount of this drawback is proportional to the quant.i.ty of malt or sugar used in the brewing of the beer, and is nearly equivalent to the duty originally paid on such malt or sugar. It is computed according to the following scale:--For every barrel, or 36 gallons of beer, the original gravity of which was not less than 1040, a drawback of 4_s._ 3_d._, and for every additional 5 degrees, from 1040 to 1125 inclusive, a further sum of 6_d._ per barrel.

SOLIDIFIED WORTS, made by a licensed brewer, from malt or sugar, or malt and sugar, a drawback of 2_s._ 10-5/100_d._ per 28 lbs.

MALT. Under certain restrictions, a drawback of the duty charged, after deducting 7-1/2 per cent. of the measured quant.i.ty.

SPIRITS, from 10_s._ to 10_s._ 3_d._ per proof gallon.

In all cases samples are taken by the Custom House officer, and forwarded to the Inland Revenue laboratory, where they are examined previous to the payment of the drawback.

=EXPRES'SION.= In the _useful arts_, the mechanical operation by which a fluid contained in the pores or cells of a solid is pressed out or expelled. Many of the fluid substances employed in pharmacy and chemistry are obtained by expression. Thus, the unctuous vegetable oils, as those of almonds, linseed, &c., are procured by submitting these substances to powerful pressure between iron plates, which are either made warm, or the bruised seeds are previously exposed in bags to the steam of boiling water. The juices of fresh vegetables are also obtained by expression. The substances are first bruised in a marble mortar, or, on the large scale, in a mill, and immediately submitted to the press, to prevent them pa.s.sing into a state of fermentation, which would injure the quality of the product. Fruits which contain highly flavoured or fragrant seeds, or which have rinds containing essential oil, are generally deprived of them before being sent to the press. The subacid fruits are also allowed to lay together for some days before pressing them, as the quant.i.ty and quality of the product is thereby increased. The fluid matter absorbed by the ingredients employed in the preparation of tinctures, infusions, decoctions, extracts, &c., is generally obtained by powerful pressure.

Expression is also frequently had recourse to for the purpose of obtaining solids in a state of purity, as in the expulsion of olein from stearin, water from bicarbonate of soda, &c. On the small scale, the common screw-press, or one of like construction, is usually employed; but the power thus obtained is insufficient to expel the whole of a fluid diffused through the pores of a solid. Hence has arisen the use of the hydraulic press, which is now almost alone employed on the large scale. In all these cases the substances are placed in bags made of haircloth, or coa.r.s.e canvas, previously to their being submitted to pressure. For tinctures and like pharmaceuticals, a small screw-press (TINCTURE PRESS) made of 'galvanised' or tinned iron, and varying in capacity from 1 quart to several gallons, is employed.

=EXSICCA'TION.= See DESICCATION.

=EX'TRACT.= _Syn._ EXTRACTUM, L. Among _chemists_ this term is understood to apply to the residuum of the evaporation of aqueous decoctions or infusions of vegetable matter. In _medicine_ and _pharmacy_, it has a less definite signification, being applied to various preparations obtained by evaporating the expressed juices, or the decoctions, infusions, or tinctures of vegetable substances, until a ma.s.s, of a solid or semi-solid consistence is formed. Extracts vary in their nature and composition with the substances from which they are prepared, and the fluids employed as solvents. When water is employed as the menstruum, the products (AQUEOUS EXTRACTS, WATERY E.; EXTRACTA AQUOSA, E. SIMPLICIORA, L.) usually consist of gum, starch, sugar, alb.u.men, extractive and saline and other matter, along with the peculiar principles on which the medicinal virtue of the vegetable depends. When spirit is employed as the solvent, the products (ALCOHOLIC EXTRACTS; EXTRACTA ALCOHOLICA, L.) contain most of the substances above enumerated, except the gum and starch, together with several other substances which are soluble in spirit, but which are either wholly or nearly insoluble in water; as resins, essential oils, and the proximate principles of vegetables. These preparations, with scarcely an exception, are considerably more powerful than the aqueous extracts of the same vegetables. In some cases proof spirit or under-proof spirit is employed, when the extracts (SPIRITUOUS EXTRACTS; EXTRACTA SPIRITUOSA, L.) generally possess properties between those of the above. In other cases, dilute acetic acid or acidulated water is employed as the menstruum, when the products (ACETIC EXTRACTS; EXTRACTA ACETICA, L.) possess much greater activity than when prepared with water; and would in many cases prove fatal, if exhibited in doses as large as those of the aqueous extracts.

Still more active extracts are obtained by a combination of the last two menstrua. According to Ferrari, plants treated with rectified spirit of wine, mixed with 1/36th part of acetic acid, yields extracts of remarkable activity. On the Continent ether is sometimes used as the menstruum for the active principles of certain substances, as cantharides, cubebs, worm-seed, &c. (ETHEREAL EXTRACTS; EXTRACTA ETHEREA, L.) The term 'simple extract' is applied to an extract prepared from a single plant or vegetable substance, and the term 'compound extract' to one prepared from two or more of such substances. The FLUID EXTRACTS (EXTRACTA FLUIDA, L.) of modern pharmacy are those which are only evaporated to the consistence of a thin syrup, and then mixed with 1-10th to 1-8th of their volume of rectified spirit.