the former of these arts enable us to ascertain the fituation of places, by fixing their latitude and longitude; and by help of the latter, we conduct our fhips from one port to another with fafety and expedition; to thefe noble fciences we are indebted not only for our increase of knowledge by travelling to foreign parts, but also for those immense riches which are frequently acquired by the induftrious merchant, and other traders among commercial people; and therefore, as our author obferves, are neceffary to be known for the fake of trade. But neceffity may be understood two ways, either for abfolute need, without which a thing cannot be; or merely for a conveniency, without which a thing cannot well be. Now it is certain, that many places are fo poor, as not to be able to maintain a populous nation, without the help of foreign trade, at this time when the world is grown fo full of people. In this cafe, there is an abfolute neceflity for navigation to carry on the business of merchandizing, without which the inhabitants could not live.'

The work before us is divided into three parts, confifting of geography, navigation, and dialling; in the former of thefe, we have an investigation of the figure of the earth, both as a sphere and spheroid, several properties of the sea, the origin of fprings and rivers; alfo a method of finding the dif tances of places, and making maps; to these articles are added, the use of the terreftrial globe, exemplified by the folution of feveral important problems of the sphere, and a copious table, exhibiting the latitude and longitude of near two thousand of the most remarkable places in the four quarters of the earth.

In the second part, which treats of navigation, Mr. Emerfon has refolved the feveral cafes thereof in the common way, and also according to the fpheroidical figure of the earth, to the former he gives the preferetice, and very juftly obferves, the latter is rather a matter of mere fpeculation, than any real ufe at fea; for in a day's run, the neceffary calculations being made by either method, will have no fenfible 'difference. And a ship mult reckon her way every day, and fo day after day, through the whole voyage. And when an observation is had, this sweeps away all irregularities from every cause, and fets all right, as far as there is à poffibility to do it; and furely, an obfervation is the only thing to be depended on in a reckoning, and ought never to be neglected; and therefore, as no apparent advantage is got by this way of failing, it may be set aside, and the more fimple and eafy method by the sphere continued in ufe. For who will think it worth their while to spend a deal of fuperfluous time and labour, to obtain a degree of accuracy, which can never be wanted? NoVOL. XXXI. February, 1771. body

K

body will, but fuch are fond of novelties, and therefore, they prefer fuch things becaufe they are new, though they have no advantage above other methods, but a manifeft difadvantage of embarraffing the calculation, and making more work for the failor; for which, I believe, he will never thank them.'

Our author concludes this fecond part with the following remark. To complete the art of navigation, these three things are abfolutely neceffary; the variation of the compafs, the latitude of the fhip, and the longitude of it. The first may be found by an amplitude, or azimuth; the fecond is known from the fun's meridian altitude; the third is ftill a fecret, and likely to continue fo. For, though many thousand pounds have been paid for the pretended discovery thereof, I doubt, we shall still remain juft as wife as we were before the discovery; except the ill fuccefs of it happens to teach us fo much wit, as to take better care of our money for the future. And, indeed, all unlikely ways and means for this purpofe, have been propofed and profecuted; whilft the only probable method is never thought of, or quite neglected.'

The third and laft part of this work contains a complete treatife of dialling, wherein the foundation of that art, and the general properties of dials, and dial-planes, are explained upon the cleareft principles; the rules for calculating all the requifites in drawing horizontal, vertical, declining, or reclining dials, rendered eafy to be understood, and the method of defcribing the common furniture of thofe dials, is the most concife and elegant of any we remember to have yet feen.

Before we conclude this article, we fhall, in juftice to the author's reputation, endeavour to obviate a feeming difficulty which occurs at p. 34. of the geographical part, where, in Cor. 1. it is faid, that the length of a pendulum vibrating feconds, increases from the equator to the pole, as the force of gravity increases, that is, as the fquare of the cofine of the latitude.' But it is evident, the cofine of the latitude, and, confequently, its fquare, decreases from the equator towards the pole; therefore, we apprehend, it is by an error of the prefs, rendered fquare of the cofine, instead of square of the right fine; and, indeed, the demonstration at p. 26, and the table of the lengths of a pendulum to vibrate feconds, at p. 35, feem to indicate the fame thing: these corrections being made, it will appear, that the increase of gravity, in going from the equator to the pole, is directly as the fquare of the right fine of the latitude, and the length of a pendulum vibrating feconds, increafes from the equator to the pole in the fame proportion, which agrees exactly with Newton, Sterling, M'Laurin, Simpson, and other eminent mathematicians.

VI. A Voy

great modefty and candour, difapproves of the ufe of leaden cifterns as refervoirs; having observed the cistern at Bath to be greatly corroded on its infide.

• The effects of lead on the human body are well known: "Obftinate conftipations, violent colics, pains and contractions of the limbs, tremors and refolutions of the nerves, and flow wafting fevers, are the confequences of this metal taken internally, and of the fumes to which the workmen are exposed in the fufion of this metal, in the way of business ;" and even the external application of ceruffe has been known to produce this effect. This metal, however, is generally thought not to be foluble in the vitriolic acid, unless in a boiling heat; and this feems true with regard to the fixed; but as to the volatile, it is by no means to be depended on, as that will act on lead in an inferior degree of heat; and though its attraction to metals does not feem to be fo ftrong, yet it diffolves them in much larger proportion than the other.

After having given the above account of the effects of this pernicious metal, we should be forry to infinuate any fufpicion of its presence in these falutary fprings. Nevertheless, the cistern, which serves as a reservoir for the spring at its first rife, appears plentifully corroded on its infide, by the long furrows which are visible in every part of it. This proves the poffibility of fuch an impregnation, though, probably, its proportion there is too fmall, or perhaps counteracted by fome other qualities of the waters, to work any obvious effects on the human body. This, however, is, by no means, a justification of the ufe of any thing liable to give an impregnation of this fort in the lightest degree. A portion of feveral metallic fubftances, almoft too minute to be difcerned, is capable of working great changes in the human frame; and among these lead claims the chief place, and is perhaps the moft dangerous, as it frequently works by flow, and almost imperceptible degrees, and has often compleated the mifchief before the person was fenfible of his danger, or to what cause to attribute his malady. The noted colic at Amfterdam was of of this kind, which for a long time eluded the fearch of the learned with refpect to its caufe; and it feems probable, from fome ingenious experiments, by Dr. Baker and others, that the Devonihire colic proceeds from the fame origin.

If to this it should be objected, that we have no accounts of any fuch effects produced by the Bath waters, and that, on the contrary, they have been proved to be very efficacious in the cure of these very difeafes, we may reply, that the action of the water on this metal has been fufficiently proved, and that it is poflible, that the unfavourable fymptoms fometimes

produced on drinking them, which we know not how to account for otherwise, may be produced by fome fuch impregnation; as this metal, though its effects are sometimes latent, is feldom inactive. It may be, perhaps, owing to this caufe, that fome diforders of the fpafmodic kind, as the opisthotonus, feem fometimes rather enhanced by drinking the waters, when bathing alone is of great fervice. This may likewise occasion the retardation, and fometimes the failure of cure, of many bowel 'disorders; and the obftinate coftiveness, so much complained of on drinking the Bath waters, which is a constant effect of that mineral, makes this conjecture not improbable. Effes, when flowly produced, and the reasons not self-evident, are often neglected, or attributed to unavoidable caufes, or circumstances to which they do not belong. The noted colic at Amsterdam had many causes affigned for it, before the true one was discovered; and it is poffible, that this quality in the Bath waters may not be originally inherent in them, but perhaps owing to fome accidental circumftance of this nature.

6 From an examination of their contents, we can discover nothing to which this effect can rationally be afcribed; and, if we reafon from analogy, all the fulphureous preparations tend rather to loofen than bind the body. An eminent and ingenious writer has cautioned against the use of lead in our common pumps, as he fays, that although lead may not be obviously soluble in common water, that a portion of it may be abraded, and fo minutely comminuted by the working of the pump, as to be fufpended in water, and thus capable of being received into the human body. If this caution was well founded, as to laying afide the use of lead in common pumps, how much stronger will it be applicable in this inftance, where the pump is worked daily many hours together, and the abrafion confequent on it proportionably greater, and the very water drawn by it capable of holding it in a state of solution? If it be farther alledged, that no lead appears to be found in the waters, even by our own experiments, we may answer, that this metal is fufficiently proved to be acted on by the ef fect beforementioned to be produced on the reservoir; and though the proportion contained in any quantity of water capable of coming under our examination, might elude a discovery by a chemical analyfis, yet its effects on the human body might be ftill poffibly exerted. This was the cafe at Amfterdam before quoted, where, though the diforder was undoubtedly owing to this caufe, and its proportion vaftly larger than it could be in this inftance, it was ftill fo minute, as to be fcarce difcoverable by a chemical examination,

' On

are filled with tigers and crocodiles; and hazarded my life in China; (where the heat of the fun on barren hills, robbers on the roads, and petulant children in back streets, are continually annoying a foreigner); and landed on the island of Afcenfion, where the fun hatches the eggs of the tortoifes, and in a fhort time ruins the conftitution of the most healthy. On the whole, however, I have no reason to be forry for my voyage, from the kind reception with which the directors of the Eaft India company have honoured me on my return: the fame year they gave me leave to go on a fecond voyage, which fome intervening obftacles obliged me to lay

afide.'

These two volumes contain, with the travels of Mr. Ofbeck; a voyage to Suratte, China, and Java, by Mr. Toreen, chaplain to a ship in the Swedish Eaft-India company's service; and a short account of the Chinese husbandry, by Charles Guftavus -Eckeberg, captain of a fhip in the fame fervice. These gentlemen, likewife, are curious obfervers of nature and art; their works deserve to be claffed with those of our author. Toreen was a man of diftinguished capacity and learning. He left Gottenburg in the quality of a chaplain to an East-Indiaman, to enlarge his knowledge. That he might make philofophical obfervations with more accuracy, he went first to Upfal, that he might improve himself by the inftructions of the celebrated Linnæus. While he was abroad, he collected many scarce plants, which he prefented to his mafter in natural history, who named the Torenia Afiatica, after its difcoverer. The feries of letters from November the zoth, 1752, to May 3, 1753, which he published on his return, are tranflated in the fecond volume of this work. He died near Nafinge, in Sweden, on the 17th of Auguft, 1753.

The Faunula, and Flora Sinenfis, which are added to this collection, are, Effays towards a Catalogue of Chinese Animals and Plants.

The principal articles of the first volume are, Mr. Ofbeck's account of Spain, the Canary-Ilands, Java, and a great part of his account of China. His obfervations in both the volumes may be termed a philofophical journal. Like a faithful narrator, he trusted not to his memory; but committed his remarks to paper as foon as he had examined their objects. His book is an agreeable, and well-arranged mifcellany; and though it principally treats of natural curiofities, and particularly of plants, it likewife comprehends the arts, manners, government, and religion of the countries which he vifited.

We beg leave to recommend in general his philofophical difquifitions to those who take pleasure in ftudying the operations of nature; we fhall extract his account of the three principal fects of religion in China, as a fpecimen which will afford amufement to most of our readers.