MECHANICS. 253 MECHANICS OF DEVELOPMENT. following works, all of wliioh are standard, can be recommended to the student of mechanics: Mach, Science of Mccliaiiics (Eng. trans., Chi- cago, 18!)3), a critical and historica! discussion of the principles; Ziwet, Theoretical Mechanics (New York, 1804), an elementary te.t-book of the best type; Love, Theoretical Mechanics (Cambridge, 1897), a most critical treatment of the fundamental principles; Routh. Elementary Rigid IJt/nantics (London, 1882); id., Adeanced Riyid Dynamics (London, 1884) : id., Statics (2 vols.. Cambridge. 181)2) ; id., Dynamics of a Purtieir ( ('anil. ridge. IS'.tS). MECHANICSBURG, m«-kan'lks-bflrg. A borough in Cumberland County, Pa., 8 miles west of Harrisburg; on the Cumberland Valley Rail- road (ilap: Pennsylvania, D 3). It is the seat of Irving College (Lutheran), and has a public library. The city is surrounded by an agricul- tural and iron-mining country, is an important shipping point for iron ore and a depot for sup- plies for the iron region, and manufactures spokes, wheels, carriages, and foundry and ma- chine-shop products. The government is vested in a maj'or, elected every three years, and a council. Mechanicsburg was settled in 1800, and was incorporated as a borough in 1828. Popula- tion, in 1S90, .•^CiOl; in 1900, 3841. MECHANICS' LIEN. A statutory lien or charge upon real estate to secure payment for work and labor performed on, or materials fur- nished for, Iniildings or other improvements thereon, at the request or with the consent, ex- press or implied, of the owner. Under the early English law no liens on real estate were recog- nized, as it was against the policy of the feudal system to permit a tenant thus to charge land which he held of his feudal lord, who in turn held of tlie King. After the feudal system was abolished, lands might be charged with liens by express agreement of the owner, and this became common in the form of mortgages. Courts of equity also recognized certain agreements in the nature of mortgages. Therefore, there are no common-law liens on real estate. By statutes, however, several liens were created, such as judgment liens, and liens for taxes and assess- ments. With the development of business cus- toms much work which was formerly done by persons acting as servants for a master came to be performed by independent contractors who stood on an equal footing with those who en- gaged them. For tlie protection of such con- tractors and of material men whose wares are used in buildings and other improvements on real estate, the statutes loiown as 'mechanics' lien laws' have been enacted in all the United States and in Canada, but not in England. There was a precedent by analogy for such laws in the common-law liens of artisans on personal prop- erty for labor bestowed on it, such as the re])air of a wagon or a pair of shoes. Somewhat similar liens on real estate were also recognized and protected by the civil law. The theory on which mechanics' liens are given by statute is that the value of the real estate has been increased by the addition of the improvements on which the work was performed or materials furnished, and that the property should accordingly be held subject to such claims. This creates a preference of these claims over those of unsecured creditors of the owner, but a mechanics' lien is subject to valid prior liens on the real estate, such as mortgages, judgments, ta.xes, etc. The term me- chanics' lien is used in a general sense to cover all liens for labor, whether skilled or unskilled, and to describe liens for materials furnished. These liens give a right to look to the property for compensation, but do not create a personal claim against the owner. As a general rule, the lien attaches both to the building or improve- ment and to the land on which it is erected : but if the improvement is placed on the land without the owneis consent the lien will not extend to the land, but will cover the improvement to the extent of the interest of the person who ordered the work and materials. The lien only attaches to the very property on which the work was done, and will not affect the other real estate of the owner. A mechanics' lien may be tiled against any title or interest in real estate, even though it is quite limited, as a lease for a year, pro- vided it is such an interest as may be sold on execution. The statutes in the different States vary in their provisions as to the character of the im- provements which will serve to raise a lien. In general, however, such liens will attach to the real estate where any structure in the nature of a building is constructed, altered, or repaired. In some States the right is extended to cover the erection of fences, laying pipes, building sewers, grading, terracing, or sodding the land, and all other improvements which may he said to benefit the land. The idea of benefit is usually con- sistently followed, in that the lien does not at- tach where buildings are torn down or moved from the land. In most States only a person who does work or furnishes nurterials at the re- quest of the owner is entitled to protect himself by a mechanics' lien. However, in a number of States, subcontractors, that is. those who work or furnish materials for the one who contracts directly with the owner, are allowed to file direct or subordinate liens against the property. As a general rule the work to which the owner is entitled under a contract must be entirely performed before the contractor can file a lieu, but where an owner defaults in his payments or otherwise breaks his part of the contract, the right to file a lien usually attaches at once. In order to perfect a mechanics' lion the statutes of most jurisdictions provide that a notice set- ting forth the names of the owner and the party claiming the lien, the character of the work done, a description of the premises, the total contract price, the amount paid thereon, the amount still due. and the date when the last item of work was performed, shall be filed in the county clerk's office and a copy thereof served on the owner of the property affected. In a number of the States this lien attaches and relates hack to the time of the commencement of the work upon its being filed, and is prior to all liens sub- sequent to that time, but it is hardly the general rule, as they usually attach and take precedence according to the order of their being filed. The statutes of the States vary in their details as to ])rocedure. time of filing, etc.. and must be consulted to ascertain those particulars. .See GAR^'rSII^rK^"T: Lten: ifouTOACE. MECHANICS OF DEVELOPMENT.. This term, or 'Entwicklungsmechanik' of the German embryologists and cytologists. is in frequent use. sussested by the chan<res undergone dur- ing cell-division (see Mitosis) and also in the
