650 PRESIDENTIAL ADDRESS
suppose, still in doubt, are " Globe lightning " and " Will of the wisp." The evidence for globe lightning is fairly substantial, but in the judgment of many scientific men is outweighed by the absence of support in laboratory experience. At one time I was more disposed to believe in it than I am now, in view of the great extension of electrical experimenting during the last thirty years. Kelvin thought it might be explained as an ocular illusion. By a lightning flash the retina is powerfully impressed, it may be excen-trically, with the formation of a prolonged positive "spectrum" or image which, as the eye tries to follow it, appears to sail slowly along. Some seconds later, the arrival of the sound of thunder causes a shock, under which the luminous globe disappears and is thought to have burst explosively. I think this explanation, which would save the good faith and to some extent the good sense of the observers, deserves attention.
Then again the Will of the wisp, for which I take it there used to be plenty of evidence. I have been told by the Duke of Argyll—the friend and colleague of Gladstone—that in his youth it was common at Inveraray, but had been less seen latterly, owing, lie thought, to drainage operations. Chemists will not readily believe in the spontaneous inflammation of " marsh gas." but I have heard the suggestion made of phosphoric gases arising from the remains of a dead sheep that had got entangled.
The truth is that we are ill equipped for the investigation of phenomena which cannot be reproduced at pleasure under good conditions. And a clue is often necessary before much progress can be made. Men had every motive for trying to understand malaria. Exposure at night on low ground was known to be bad; and it had even been suggested that mosquito nets served as a protection; but before Pasteur, and indeed for some years after, it seems never to have occurred to any one that the mosquito itself was the vehicle. Sir A. Geilde has remarked that until recent times the study of the lower forms of life was regarded with something like contempt. Verily, the microbes have had their revenge.
But when all this has been said we must not forget that the situation is much worse when it is complicated by the attempts of our neighbours to mislead us, as indeed occasionally happens in other matters of scientific interest where money is involved. Here also the questions before this Society differ from most of those dealt with by scientific men, and may often need a different kind of criticism.
Such criticism it has been the constant aim of the Society to exercise, as must be admitted by all who have studied carefully our published matter. If my words could reach them, I would appeal to serious inquirers to give more attention to the work of this Society, conducted by experienced men and women, including several of a sceptical turn of mind, and not to indulge in hasty conclusions on the basis of reports in the less responsible newspaperng to say ta them. Is—(i.e. believers).