204 On the Antilunar Tide, [March, 



rating the upper or insulated coated sheet from the under ones, and 

 drawing a spark from it before it was put back in its place. 



These experiments will succeed best when the bend or fold in the 

 middle of each sheet will have been made to disappear (which may 

 be done by wetting that part of the paper, and letting it dry under 

 some weight, or by ironing)^ as then the sheets by lying more flat 

 On one another will better exclude the air, which would in a great 

 degree lessen their electrical energy. 



The Indian rubber employed should be of the thick kind, and 

 that side of it which bears the mark of the knife be brought in 

 contact with the paper. This gum is in itself slightly electrical. 



Drawings made on paper with lead pencil will, like those formed 

 on glass with tin foil, become luminous when an electrical discharge 

 passes through them : the whole surface of the black lead coating 

 will sometimes appear a mass of light. 



1 am. Sir, your obedient humble Servant, 



Phii-ip Walsh. 



Article IX. 



On the Antiiunar Tide, By John Campbell, of Carbrook, Esq. 



F.R.S.E. 



(Continued frtm p. 131.) 



This theory, it will be observed, rests on the supposition, that, 

 at the conjunction the moon is acted on by the difference between 

 the forces of the sun and earth ; and that she is at the opposition 

 affected by the sum of these forces. The other theory; similar to 

 the tlieory of the tides, agrees in supposing the moon at the con- 

 junction, to be affected only by the difference between the forces 

 of the sun and the earth, but at the opposition, instead of ascribing 

 the increasing curvature to the increase of gravity produced by the 

 joint action of the two forces, it ascribes it to a diminution of gra- 

 vity produced by their difference.* These theories cannot be both 

 true, for they are contradictory to each other ; but it will not re- 



* M. Laplace slates (his very broadly. •' Ainsi, dc toutes les actions du soleil 

 surlahine, dans le cours de sa revolution synodiqup, il resulte un force moyeune, 

 dirig^e suivant le rayon vecteiir limaire, qui diminue la pesanteur de ce satellite." 

 Stfsi. p. 228. How tliis acute philosopher should adopt an opinion, that in any 

 sitnation, coincident attractions should act as opposite attractions, and in any 

 degree destroy one another, would be inconceivable, were it not remembered, 

 that his mind was directed to an analysis of intricacy sufficient to absorb all hit 

 attention. One would equally wonder, that the principles of pressure, or re- 

 gistcd attraction, did not occnr to him as a certain and necessary cause of an anti- 

 Jnnar tide, were he not persuaded of the truth of that philosopher's own remark on 

 D'Alcmhen's discovery of the resolution of the law» of molion into that ^f 

 equililiriiiin. " Que les ide^s le plus simples lont presque toBjours celles qui 

 s'offrcBt lei dcjnii^res a Tetprit boinain." 



