140 Hydraulic Illusions. 



the nucleus is concerned, there is much resemblance to the 

 comet of last year. The tail, which arises irregularly from only 

 a part of the breadth of the coma, is short, -as yet, in propor- 

 tion to the brightness of the head. At present, no conclusion 

 can be safely formed as to the period of this comet, whose orbit 

 is said to have a slight resemblance to that of the year 770. 

 Detailed observations, which have hitherto been but few, from 

 the pertinaciously adverse condition of the sky, will be given in 

 a future number. 



HYDBAULIC ILLUSIONS. 



BY W. B. TEGETMEIEE. 



Those visitors to the metropolis who accept Dr. Johnson's invita- 

 tion, and take a walk down Fleet Street, may have noticed the 

 small crowd of wondering gazers usually assembled around a 

 shop window a few doors west of Temple Bar. The object of 

 attraction being, not the exterior of the earthenware filters 

 vended by the occupant, but a series of hydraulic contrivances 

 and designs, the most attractive of which is a perpendicular glass 

 tube, some six feet in length, up which is seen passing in endless 

 and regular succession a series of bubbles of air, as unsubstan- 

 tial and as interminable as the line of shadowy kings that passed 

 before Macbeth. 



The mechanism by which this exceedingly effective and 

 pretty contrivance is produced is entirely concealed ; and as the 

 occupant of the warehouse astutely declines to afford any infor- 

 mation on the subject, the matter has remained for several years 

 one of the unsolved enigmas of the town. 



That the means adopted to produce the result are not gene- 

 rally known is evident from the fact, that the design has not 

 been imitated, which, from its attractive character, would have 

 been the case had the means by which it is effected been 

 understood. 



Scientific knowledge is not, however, the exclusive property of 

 any one individual ; and as Mr. Lipscomb has had for a very long 

 period the benefit of this attractive advertisement, we have no 

 hesitation in laying bare the concealed mystery, at the same 

 time giving him every credit for the knowledge displayed and 

 the ingenuity manifested in the contrivance. 



The ascent of these bubbles is obviously produced by means 

 of an apparatus known to chemists under the name of an aspi- 

 rator, from its being employed to draw a current of air or gas 

 through any tubes or vessels along which it may be required 

 to flow. 



