172 ELECTRICITY* 



A E' D, will have received oscillations at the Same Ino- 

 ment, they will form as many curves', altogether forming 

 a kiild of Cross Or star. It is to be observed that the 

 lines at Vest are not described by heaps of dust, but are 

 surrounded by them. These lines cannot be described 

 in the ordinary manner by the scattered sand, because it 

 is elastic, and its particles are too considerable for each 

 one to continue jin niotion*untiII it finds a tranquil and 

 appropriate place. If two grains of sand be thrown 

 upon a square of glass, thrown into motion by means of 

 a bow, the experiment will confirm what has been just 

 laid down. Consequently, the lines of powder must not 

 be confounded with the lines of repose, which are deno-* 

 minated lines of knots. Tlie powder ^ on the least motion^ 

 detaches itself from the lines of knots, as is seen in the 

 experiment ; but it is very difficult to detach it from the 

 lines of sand. Hence we may suspect that the undulatory 

 movement excites a degree of electricity, which is doubt- 

 less negative in the lines of knots and positive in those 

 ' of repose, since the negative lycopodium is attracted by 



it. It is pfrobable that all philosophers are acquainted 

 with what Ritter has said on this subject in Voigt's 

 Magazine. 



LECTURES ON SURGERY. 



Mr. A. CARLISLE, F.R.S. F.L.S. and Surgeon to 

 the Westminster Hospital, intends to deliver a Course of 

 Lectures bn the Art and Practice of Surgery, in all its 

 Branches, during the present Season, at his House in 

 Soho Square. 



The History and Treatment of the Diseases and Affec- 

 tions, which belong to the Province of Surgery, will be 

 fully investigated , the several Methods of Practice ex- 

 amined, and accompanied with such Observations as the 

 Lerturer's Experience may furnish. The various Chi- 

 rurgical Operations will be demonstrated, and the Ana- 

 tomy of the Parts explained, together with the Devia- 

 tions, Accidents, and Difficulties which occasionally hap- 

 pen, and the Rules to be observed in each Instance. 



An Introductory Discourse, (open to all Students) 

 comprising the Plan of these Lectures, will be given on 

 Monday, October 13, at Seven o'Clock jn the Evening. 

 And the Lectures will be continued on Mondays, Wed- 

 nesdays, and Fridays, at the same Hour — Tickets for 

 the Course, Three Guineas ; perpetual, Five Guineas. 



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