Some Considerations Touching a Letter in the Journal des Scavans of May 24. 1666

bright Sun, or that it might be some dust in the Aire. The great Microscope being fitted in the day-light for this piece of Fish, we examin'd it that night, and it yielded no light at all, either by the view of the Glass, or otherwise. Finding it dry, I thought that the moisture of Spittle, and touching of it, might cause it to shine: and so it did, though but a very little, in a few small sparks, which soon extinguish'd. This we saw with the bare eye; not in the Glass. The Fish were not yet fetide, nor insipid to the best discerning palats: And I caused two Fish to be kept for further Tryal, two or three days longer, till they were fetide in very hot weather; and then I expected more brightness, but could find none, either in the water, by stirring it, or in the Fish, taken out of the water. And some Trials I made afterwards with other boil'd Mackrels (as is abovesaid) with like pickle, but fail'd of the like success. This season serves for many Trials in this kind, and by better Microscopes, or better ordered. And in these Vulgarities we may perhaps as well trace out the cause and nature of Light, as in Jewels of greatest value, &c. Some Considerations Touching a Letter in the Journal des Scavans of May 24. 1666. In Num. 9. of these Transactions were publish'd the Schemes and Descriptions of certain Ways of Sounding the Depth of the Sea without a Line; and of Fetching up Water from the bottom of it; together with some Experiments already made with the former of these two Contrivances. The Author of the French Journal des Scavans found good, to insert them both in his Journal of May 3. but in another of May 24. intimates, that the said Schemes and their Descriptions are not very clear and intelligible (he means, that they were not well understood by French Readers) proposing also some Difficulties, relating to that Subject, and esteemed by him necessary to be satisfied, before any use could be made of the said Instruments. Upon this occasion, the Author of these Tracts thinks fit, here to represent, First, First, That Englishmen and such others, as are well versed in the English tongue, find no difficulty in understanding the descriptions of these Engines, nor in apprehending their structure, exhibited by the Figures, especially if notice be taken of the Emendation, expressed at the end of Num. 10, about the misgrav ing the Bended end of the Springing Wire (which it seems has not been noted in France, tho' the said Num. 10 is known to have been seen there a pretty while before their Journal of May 24. was publish'd). And as for the particular of the Bucket, fetching water from the bottom of the Sea, both the Figure and the annexed Description thereof are so plain and clear, that 'tis some wonder here, that any difficulty of understanding them is pretended by any, that hath but ordinary skill in Cutts and the English language. Mean while, that way, which the French Author recommends for this purpose as more simple, Videl. a Brass-Pump with double Valves, is not at all unknown in England, nor his bin left untried there; but was found inconvenient, in respect that the Valves in descending did not fully open, and give the water a free passage through the Cavity of the Vessel, nor in ascending shut so close, as to hinder the water from coming in at the top: Whereas by the way proposed in Num. 9. both is perform'd with great ease and security. Secondly, Whereas the French Author is of opinion, that 'tis unknown, how much time a Heavy Body requires to sink in water, according to a certain depth; he may please to take notice, that that hath been made out in England by frequent Experiments; by which, several Depths, found by this Method of founding without a Line, were examin'd by trying them over again in the same place with a Line, after the common way. And as to that Quere of his, Whether a heavy Body descends in the same Proportion of swiftness in Water, that it would do in Air? The Answer is, that it does not; but that, after it is sunk one or two fathoms into the Water, it has there arrived to its greatest swiftness, and keeps, after that, an equal degree of velocity; the Resistance of the water being then found equal to the Endeavour of the heavy Body downwards. Thirdly, When the same Author alledges that it must be known, when a Light Body reascends from the bottom of the water to the top, in what proportion of time and swiftness it rises. He seems not to have considered, that in this Experiment, the times of the descent and ascent are both taken and computed together; so that for this purpose, there needs not that nicety, he discourses of. Fourthly, Whereas it is further excepted, That this way of Sounding Depths is no new Invention; The answer is ready, that neither is it pretended to be so, in the often quoted Tract; it being only intimated there, that the manner of performing it, as it is in that place represented and described, is new. Lastly, To rectifie the said Author's mistake, as if the instrument of fetching up Water from the bottom of the Sea, were chiefly contriv'd, to find out, Whether in some places of the Sea any Sweet Water is to be met with at the bottom: There will need no more, than to direct him to the Book itself Num. 9. where p. 149. towards the end, the First use of this Bucket is express'd to be, to know the degrees of Saltiness of the Water according to its nearness to the top or bottom; or rather to know the constitution of the Sea-water in several depths of several Climates, which is a matter, much better to be found out by Trial, than Discourse. Neither is it anywhere argued in that Book (as the French Journal insinuates) that, because sweet water is found at the Bottom of the Sea of Babarem, therefore it must, but only that it may, be found so elsewhere. And since the same Journal admits, that those Sweet water-springs, which yield the sweet water, that is found at the said place, have been formerly on the Continent, far enough from the Sea, which hath afterwards covered them. It will be, it is presumed, lawful to ask, Why in many other places there may not be found the like? And besides, how we do know, but that there may be in other parts, Eruptions of large Springs at the bottom of the Sea, as well as there? Printed with Licence for John Martyn, and James Allestry, Printers to the Royal-Society. 1666.