IGNEOUS ROCKS. 464 IGOE'S BAND. rocks (as do nlsci the cinstic rocks), so tlmt no Hhnrp line can be drawn to separate these great divisions. t;rcat dillieulties arise in the systematic classi- fieation of ipiicmis ro<-ks. by reason of the many ways in which it is possible to describe them, and the varyin;,' iinpiirtanic which is attached to each method; hence ^rcat iliircrence of opinion exists nmiin<; petrojiraphcrs as to th<- best scheme to be adopted. On the Continent of Kurope, and espe- cially in tiermany. the inannci- of occurrence of a ro«>k. whether as a boss or batholite (q.v. ), as a dike (fj-v.). or as a sheet or flow, is given the first importance; and the n<;c of the rock, once considered paramnnnt, still retains its importance in the secondary elassitication. In America opin- ion seems to favor as bases of classification the chemical eompiisiticm. the texture, and the min- eral composition; but the future must 1k' awaited before any classification free from serious objec- tions is likely to be adopted. The almost hope- less confusion of the schemes now in use is gen- erally recognized. The reader is referred to the folhiwing works, in which are given detailed de- scriptions of igneous rocks. Consult: Kemp, Uandbook of Hocks (New York. 1800) ; Rosen- buscli, Mikronkopisrhr I'hiisiofiriiphie (/<r l/i- neralicn und Heslriiw (Stuttgart. 1800); Zirkcl. l.ehrhuch dcr I'ctrographic (l^ipzig. 1894) ; Teall. Hrilish Petrography (London, 1888). See Geoi.O(;y. IG'NIS FATUUS, fnt'fl-fls (Lat.. vain fire). A luiiiimius appc:iranec frequently seen in marshy places, in churchyanls, ami over stagnant pools. It generally appears a little after sun- set as a pale, bluish-colored tiame, varying in size and shape; sometimes it shines steailily till morning, at other times disappears, and rcap- jM'ars within abovit halflunirly intervals. It floats in air at about two feet from the ground, is sometimes fixed, and sometimes travels with great rapidity. Many efforts have l>een made to discover its cause; but .so varied arc its appear- ances and so void of any common principle, that these attempts have totally failed. Two of the various explanations offered may be mentioned here. The first is that t}ie ignis fatuus is due to phosphuretcd hydrogen gas (PH-), which pos- sesses the properly of ignitini; when.it comes in contact with dry atmosplicrie air: the gas would be generated by the decomposition of ani- mal matter present in a marshy soil. The second is that it is due to the combustion of methane, or marsh-gas, CTI„ produced by the decomposition of vegetable matter: but though this supposition satisfactorily accounts for many appearances connected with the ignis fatuus, the gas itself is not spontaneously combustible, and an addi- tional supposition becomes necessary to account for its ignition. The probable conclusion is that a nundier of phenomena, apparently similar, but arising from dilTcrcnt causes, are aggregated under the tenn ignis fatuus. The appearance of ignis fatuus is not a common phenomenon, and many distinguished naturalists who desired to investigate it have never suc- ceeded in finding it : hut it is not unfrequently seen in the north of Germany, the swamp and moorland districts in the south and northwest of England, and in the lowlands of Scotland. It is seen in the above places from the middle of autumn till the beginning of November. In former times the ignis fatuus, under the names of Will-o'-the-VVisp, .Jack-a-lantcm, Spunkie, etc., was an object of superstition an.ong the inhabi- tants of the districts where it appears, ami was believed to be due to the agency of evil spirits ntteiii[iting to lure travelers to tlieir destruction. IGNOKANCE OF THE LAW. One of the important maxims uf the eomnion law is igno- rance of the law excuses no one. It is not, how- ever, an aphorijim of universal application, nor ia it to be pressed into the service of injustice; neither does it warrant the presumption that every one knows the law. There is no such pre- Bunijjtion. It would be eontrarj- to conunou sense and reason. Yet the rule that ignorance of law shall not serve as an excuse for illegal acts or omissions is common to all systems of law, and is not only expedient, but necessary. The maxim is of prime importance in criminal law, yet here it has real or apparent exceptions. If a pers(ui is indicted for hirciny be may show that he honestly lu'licved the property to be his own. although it appeared that this belief was due to )iis ignorance of a rule of law which vested the property in another. This results, however, from the fact that he does not connnit the crime of larcenj' "unless he intended to appro- priate another [)erson"s ])roperty to his own use. Had the indicted perscm l>een sued for con- version by the true owner, his ignorance of the law would have been no excuse. In the civil action for conversion his motive, or intention, or belief in taking would be innnaterial. One who takes and uses property as his own acts at his peril. So if a person enters into an honest and fair contract he cannot, except in certain ea.ses of fraud or deieit (q.v.). absolve himself from its obligation by showing that he would not thus have contracted had he known the rule of law applicable to the transaction. in general it may also be said that a person who has paid money in ignorance of the law can- not recover it in a quasi-contract action. This means that no man will be permitted to exempt himself from a duty, or shelter himself from the con,se(iuences of infringing a prohibition imposed by law, or acquire an advantage in opposition to the legal rights and interests of another by pre- tending error or ignorance of law, .See Mistake; Qi:.si roMit.xcT. IGTJORAN'TINES (from Lat, ignomre. to be ignorant), . religious congregation of men in the Roman Catholic Church, associated for the gratuitous instruction of poor children in sacred as well as secular learning. See SCFIOOLS, Brotukh.s ok the Cubistian. IGORROTE, r'gorro'tft. A warlike people of mixed Malay-Mongoloid blood, speaking several dialects; chietly in Benguet Province, Luzon. Also any wild Filipinos of Malay blood. Vari- ants. Ygolot, Ygulut, etc. See PnitiPPiNE Isl- ands. IGOR'S (e'gorz) BAND, Song of (Russ. Sfloio o jiolkii Igorere) . The only Russian poetic- al mcmument, dating from the twelfth centurj'. It recites the unfortunate outcome of the expe- dition (118.5) of Tgor, Prince of Kovgorod-Syev- ersk. into the countrv' of the Polortsy in Southern Russia. The Prince was defeated and taken pris- oner, but later he escaped with the help of a slave. The poetic gems of the song are the lyric pas- sages depicting the grief of Nature over the Prince's capture; the lament of Yaroslavona, his-
