OBSCURANTISTS 



OBSERVATORY 



569 



the law was effected by Lord Campbell's Act, 

 which was passed in 1857, to suppress the traffic 

 in obscene books, pictures, prints, and other 

 articles. Any two justices of the peace, or any 

 police-magistrate, upon complaint made before 

 him on oath that such books, &c. are kept in 

 any house, shop, room, or other place, for the 

 purpose of sale, or distribution, or exhibition for 

 gain or on hire, and that such things have been 

 sold, &c., may authorise a constable to enter in 

 the daytime, and, if necessary, use force by break- 

 ing open doors, or otherwise to search for and 

 seize such books, &c. , and carry them l>efore the 

 magistrate or justices, who may, after givinj* due 

 notice to the occupier of the house, and being 

 satislied as to the nature and object of keeping 

 the articles, cause them to be destroyed. 



Obscurantists ('lovers of darkness;' Lat. 

 obscurare, ' to darken ' ), the name given to those 

 who are supposed to look with dislike and appre- 

 hension on the progress of knowledge, especially 

 to such as defend theological prejudices against 

 what is believed -to be scientific truth. 



Observantists. See FRANCISCANS. 



Observatory, an institution supplied with 

 instruments for the regular olwervation of natural 

 phenomena, whether astronomical, meteorological, 

 or magnetical. In some observatories all three 

 classes of observation are carried on, but in most 

 cases special attention is paid to astronomy alone, 

 and only such meteorological observations are 

 taken as are required for the calculation of the 

 effect of atmospheric refraction on the position of 

 a heavenly body ; there are, however, several 

 observatories which are devoted solely to meteor- 

 ological or magneticnl observations. 



The most important work which is canned out 

 in public astronomical observatories is the deter- 

 mination of the movement* of the sun, moon, and 

 planets among the stars ; and, as a corrollary to 

 this, the relative positions of the stars to which 

 the other heavenly bodies are referred. In early 

 times the Greek astronomers tixed these positions 

 by means of the Armillary Sphere (q.v.) and the As- 

 trolabe (q.v. ). Ptolemy made use of a Quadrant 

 (q.v.); and many centuries after Tycho Brah6 

 converted this form of instrument into an Altazi- 

 muth (q.v.), with which he made a long serif s of 

 observations of the altitudes and azimuths of the 

 heavenly bodies at the observatory which the kin;,' 

 of Denmark erected for him ; and lie also measured 

 with great assiduity their angular distances from 

 each other by means of a Sextant (q.v.). It was 

 not till the middle of the 18th century that the 

 improvement of the clock by Graham enabled 

 astronomers to rely on it for the determination 

 of right ascensions by the times of passage across 

 the meridian by means of a quadrant. A pair of 

 such instruments pointing respectively north and 

 south were erected at the Royal Olwervatory, 

 Greenwich, and used by Bradley and his successors 

 from 1750 till they were displaced by the Mural 

 Circle (q.v.). At the same time the accuracy of 

 readings was greatly increased by the invention 

 of the micrometer- microscope, which made it 

 possible to measure spaces to rug'troth of an 

 inch. Neither the quadrant nor the mural circle, 

 however, could be relied upon for accurate 

 motion in the plane of the meridian, but Krtmer 

 remedied this defect by inventing a separate 

 instrument, the Transit (q.v.). With the transit 

 and quadrant Dradley commenced that series of 

 observations of the positions of the sun, moon, and 

 planets, and of stars for reference, which has been 

 continued ever since at Greenwich, and on which, 

 in combination with less extensive series at Paris 

 and Kcmigsberg, all our tables of the motions of 



the heavenly bodies are founded. In modern 

 observatories the transit and mural circle are 

 combined into one instrument, the Transit circle 

 (q.v.). An important auxiliary to the transit- 

 circle is the chronograph, an American invention, 

 which, in various forms, is now found in all well- 

 equipped observatories, the principle in all cases 

 being the same viz. the registration on a revolv- 

 ing cylinder of paper of the times of transit across 

 the system of spider-lines of the transit-circle, as 

 well as of the seconds of the sidereal clock, by 

 means of electric currents, which pass through 

 electro-magnets when the circuit is closed either 

 by the observer or the clock, thus causing a 

 momentary attraction of a piece of soft iron, and 

 producing a corresponding mark on the paper 

 either with a pen or a steel point. This system, 

 while improving somewhat the accuracy of the 

 individual observations, admits of a large number 

 lieing made at intervals of two or three seconds, 

 and leaves the observer free to make several obser- 

 vations of zenith distance during the passage of a 

 star across the field of view. The observations of 

 stars at the observatories of Greenwich, Paris, 

 Washington, and Oxford are mainly directed to 

 the most accurate determination of the places of 

 a limited number, and the deduction of their proper 

 motions by comparison with the results obtained 

 by Bradley, Piazzi, and Groombridge ; at other 

 observatories differential or zone observations of 

 large numbers of stars have been made, with the 

 object of making a complete and tolerably accurate 

 survey of the heavens. 



A large number of observatories, chiefly in Ger- 

 many and America, are devoted to a very different 

 class of olx>ervations viz. differential observations 

 with the Equatorial (q.v.) of comets and small 

 planets as referred to comparison-stars, and the 

 search for such objects ; whilst at other observa- 

 tories, among which that of Pulkova may be men- 

 tioned, the measurement of double stars with the 

 micrometer is laid down as the chief object. Of 

 late years two new subjects have been introduced 

 in the routine of observatory work photography 

 and spectroscopv. The former was carried on for 

 many years at kew Observatory under Mr De La 

 Hue's auspices, and at his private observatory at 

 Cranford, and the work is now being continued at 

 many observatories, lioth public ami private ; the 

 latter has bi-rn taken up at a number of Italian 

 observatories, and particularly at Rome by P. 

 Secchi, and it now forms part of the regular 

 system at Greenwich ; whilst the observatories at 

 Paris, Berlin, and Vienna are equipped for these 

 physical observations, and in America and Aus- 

 tralia they are vigorously carried on at several 

 observatories Melbourne, in particular, being pro- 

 vided with a four-feet equatorial reflector for this 

 purpose, as well as for the examination of nebulze. 

 The most important work of an observatory, how- 

 ever, consists not in making observations which 

 are easily multiplied, but in reducing and publish- 

 ing them a tasK of far greater lalmur, ann requir- 

 ing far higher qualifications. However various 

 may be the observations, the mathematical method 

 of eliminating their errors is the same in all cases ; 

 and it is when such treatment is required in any 

 inquiry that it should be undertaken at a public 

 observatory, where this rigorous method will be 

 applied. 



In addition to regular astronomical observations 

 of all kinds, national observatories are usually 

 charged with the distribution of time signals, and 

 the rating of chronometers for the navy matters 

 of great practical importance, especially in Great 

 Britain, where Greenwich time is communicated 

 directly by telegraph to more than 600 towns. 



There were observatories amongst ancient 



