=ACTINISM.= _Syn._ ACTINIC RAYS; CHEMICAL RAYS. A term given to a supposed principle accompanying the heat and light of the sunbeam. Actinic rays chiefly exist beyond the violet extremity of the solar spectrum, and are characterised by the power of exciting chemical change, _e.g._, the decomposition of certain silver salts (in photography); the combination of a mixture of chlorine and hydrogen, &c. The so-called vital functions of animals and plants are also greatly influenced by the actinic or chemical rays. =ACTINOGRAPH.= An instrument for registering the intensity of the chemical influence (_actinism_) of the sun’s rays. =ACT, TOWNS IMPROVEMENT CLAUSES, 1847= (10 & 11 Vict., c. 34), The following provisions of this Act are incorporated in the Public Health Act, 1875, and refer exclusively to urban districts:—— 1. With respect to naming the streets and numbering the houses. 2. With respect to improving the line of the streets and removing the obstructions. 3. With respect to ruinous or dangerous buildings. 4. With respect to precautions during the construction and repair of sewers, streets, and houses. 5. With respect to the regulation of slaughter houses. Notices for alterations under the 69th, 70th, and 71st sections, directions under the 73rd section, and orders under the 74th section of the said Towns Improvement Clauses Act, may, at the option of the urban authority, be served on owners instead of occupiers, or on owners as well as occupiers, and the cost of works done under any of these sections may, when notices have been so served on owners, be recovered from owners instead of occupiers; and when such cost is recovered from occupiers, so much thereof may be deducted from the rent of the premises where the work is done as is allowed in the case of private rates under the Act. =AC′TUAL.= Real, effectual, absolute; as opposed to that which is merely virtual or potential. In _surgery_, a red-hot iron, or any other heated body, used as a cautery, is termed the ACTUAL CAUTERY; whilst a caustic or escharotic so employed is called the POTENTIAL CAUTERY. =ACTUAL CAUTERY.= See ACTUAL. =ACUTE′.= _Syn._ ACUT′US, L.; AIGU, Fr.; HEFTIG, HITZIG, SPITZIG, Ger. Sharp, pointed, sensitive. Applied to the senses, as acute hearing, eyesight, &c. In _pathology_, diseases exhibiting violent symptoms, and whose course is short, are said to be acute diseases. =ADAPTER.= In _chemistry_, a tube placed between two vessels (commonly a retort and receiver) for the purpose of uniting them or increasing the distance between them, so as to facilitate the condensation of vapour in distillation. (See _figure._) [Illustration]