342. It would be an error to think that this fraternal concert is unnecessary in reunions for physical mani festations more especially, and that they exclude all serious thought ; if they do not require so rigorous conditions, it is not with impunity that they are under taken with levity, and . a person would be deceived should he suppose that the concurrence of the assist ants is absolutely null ; we have the proof of this in the fact that often manifestations of this kind, even called out by powerful mediums, can produce nothing in some places. There is some reason for it, and it can only be in the divergency or hostility of sentiment which paralyzes the efforts of the spirits.
Physical manifestations, as we have said, are of great utility ; they open a vast field to the observer, for it is an entire order of unusual phenomena unfolded to his view, whose consequences are incalculable. Thus, an assembly may be occupied with very serious views, but may not attain its end, whether of study or means of conviction, if it is not placed in favorable conditions : the first of all is, not faith in the assistants, but their desire to be enlightened, without subterfuge, or deter mination to reject the evidence ; the second is the re striction of their number, to avoid the bringing together of heterogeneous elements. If physical manifestations are, in general, produced by the less advanced spirits, they have none the less a providential end, and good spirits always favor them when they can have a useful result.