SQUADRON 



SQUILL 



665 



and high social standing. The political spy, act- 

 ing in nis own country, is hard to distinguish from 

 the detective ; it will often be difficult to draw a 

 line between the spy abroad and the renegade or 

 traitor on the one hand, and the political agent. See 

 Caron, Twenty-five Years in the Secret Service (1892). 



Squadron. See CAVALRY, REGIMENT, TROOP. 



Sqnarcione, FRANCESCO (1394-1474), origin- 

 ally a tailor, hut founder of the Hadnan school of 

 painters, best known as teacher of Mantegna (q.v.). 



Square Root. See INVOLUTION. 



Squares, METHOD OF LEAST, an arithmetical 

 process of great importance for combining obser- 

 vations, or sets of observations, so as to obtain 

 the most probable value of a quantity which 

 depends on these observations. It is in fact 

 the scientific method of taking certain averages, 

 and it finds its most constant use in astronomy 

 and other physical sciences. The necessity for 

 applying the method arises from the fact that, 

 when the greatest precision of measurement is 

 sought, repeated measurements of the same quan- 

 tity do not agree. Thus, the altitude of a star at 

 culmination, if carefully measured night after 

 night by the same observer through the same 

 instrument, will in general come out a little 

 different in the different observations. All the 

 measurements will, however, lie within a certain 

 range of variation ; and if all are equally trust- 

 worthy, the arithmetical mean will give the most 

 probable value of the real altitude. The differences 

 between this mean and the individual measure- 

 ments on which it is founded are called the 

 residuals. The important mathematical property 

 of these residuals is that the sum of their squares is 

 less than the sum of the squares of the differences 

 Wtween the individual measurements and any 

 other single quantity that might be taken. Now, 

 this principle of ' Least Squares ' holds not only 

 for the simple case just described, but also for 

 more complicated cases in which one observed 

 quantity (y) is to be expressed as an algebraic func- 

 tion of another or of several independently oleerved 

 quantities (x). Here the object is to find the most 

 probable values of the assumed constants or para- 

 meters which enter into the formula. When these 

 values are calculated we can calculate in terms of 

 them and the observed z's a value of y correspond- 

 ing to each set of observations. Comparing the 

 calculated y's with the observed y's, we get a set 

 of residuals, the sum of whose squares is a minimum 

 if the parameters have been calculated according 

 to a particular process. It is this process which is 

 described as the method of least squares. Its basis 

 is found in the mathematical principles of Prob- 

 ability (q.v.). See Professor Merriman's Textbook 

 on the Method of Least Squares (2d ed. 1885), or 

 Chanvenet's smaller treatise (1879), and for ele- 

 mentary discussion any good treatise on practical 

 astronomy and geodesy. 



Squaring the Circle. See QUADRATURE. 



Squash, a term loosely used, especially in the 

 United States, for two or three kinds of Gourd 

 (q.v.), including the pumpkin. 



Squid. See CALAMARY. 



Squler, EPHRAIM GEORGE, American author 

 and archaeologist, was born at Bethlehem, New 

 York, June 17, 1821. From 1841 to 1848 he 

 was a newspaper editor, latterly in Ohio ; and 

 hia attention being attracted to the antiquities 

 of the Scioto Valley, he made an exploration 

 of similar monuments through the Mississippi 

 Valley, an account of which was published in 

 vol. i. of the Smithsonian Contributions to Know- 

 ledge ( 1848). He made similar explorations in New 

 York in 1848; and next year being appointed 



charge if affaires to the states of Central America, 

 he used his official position as a means of making 

 extensive geographical and archaeological explora- 

 tions in those regions. For his researches he re- 

 ceived the gold medal of the French Geographical 

 Society. In 1853 he surveyed a railway route 

 through Honduras, and extended his archfeological 

 inquiries. In 1863 he was appointed U.S. commis- 

 sioner to Peru ; and afterwards he edited Frank 

 Leslie's publications. He died in Brooklyn, 17th 

 April 1888. Among his works are Nicaragua : its 

 People, Scenery, and Ancient Monuments (1852); 

 Serpent Symbols ( 1852) ; Notes on Central America 

 (18o4); Waikua, or Adventures on the Mosquito 

 Shore (1855) ; Central America ( 1857) ; and Pent: 

 Explorations in the Land of the Incas ( 1877 ). 



Squill (Scilla), a genus of bulbous-rooted 

 plants of the natural order Liliaceas, with radi- 

 cal leaves, and flowers in terminal racemes or 

 loose corymbs. The species, which are numer- 

 ous, are natives chiefly of the Mediterranean 

 and Caucasian regions. Three are natives of 

 Britain, S. verna, which is abundant on the 

 east coast of Ireland, the west and north coasts 

 of Scotland, more sparingly on the east coast 

 of Scotland, and very locally in north-eastern 

 England ; S. autumnalis, which is confined to some 

 of the southern counties of England ; and S. nutans, 

 the wood-hyacinth or blue-bell of England, which 

 is very abundant in most parts of Great Britain 

 and Ireland. These and many exotic species are 

 frequently cultivated for the sake of their beauty 

 in British gardens. 



Very different in habit from these, and now- 

 separated from the genus, is the Officinal Squill 

 ( Urginea Scilla, or mantima ; formerly called 

 Scilla maritima), a native. of the sandy shores of 

 the Mediterranean, which has a scape from two to 



A, Scilla verna; B, Officinal Squill ( Uiijinea Scilla) : a, 

 plant with flowering scape in blossom ; 6, plant with 

 full-grown leaves. (From Bentley and Trimen.) 



four feet high, with a raceme of many whitish 

 flowers and large leaves. The bulb is of the size 

 of a man's fist, or sometimes as large as a child's 

 head, and contains a viscid mice so acrid as to 

 blister the fingers if much handled, whilst the 

 vapour arising from it irritates the nose and eys. 



