VOL. L.] PHILOSOPHICAL TRANSACTIONS. \4g 



and from these to the blood, differ in nothing from what we observe of the other 

 lymphatics. Their lymph, in the mean time, is without doubt or controversy 

 supplied from the cavity of the intestines ; being the watery moisture continually 

 exhaled there for the purposes of digestion, and for the preservation of the ali- 

 mentary canal, and as continually taken up by the roots or extremities of these 

 vessels, in order to be carried back to the blood, after it has performed its office 

 in the bowels. Let it also be remembered, that these vessels, in other places of 

 the body, are generally, when we trace them, lost in muscular, tendinous, or 

 membranous parts ; and then, it is presumed, it may fairly, and with a good de- 

 gree of evidence, be concluded, that the lymphatics of the body, in general, 

 have their origin among the little cavities of the cellular substance of the muscles, 

 among the mucous folliculi of the tendons, or the membranous receptacles and 

 ducts of the larger glands ; that their extremities or roots do, from these cavities, 

 imbibe the moisture exhaled there from the ultimate arterial tubes, just as the 

 lacteals (the lymphatics of the mesentery) do on the concave surface of the in- 

 testines: and that the minute imbibing vessels, by gradually opening one into 

 another, form at length a lymphatic trunk, furnished with valves to prevent the 

 return of its fluid, and tending uniformly, from the extremities and from the 

 viscera, to reconvey to the blood that lymph, or that fine stream, with which 

 they are kept in perpetual moisture; a circumstance indispensably necessary to 

 life and motion: while, at the same time, the continual reabsorption of that 

 moisture by the lymphatics is no less necessary, in order to preserve the blood 

 properly fluid, and to prevent the putrefaction, which would inevitably follow, 

 if this animal vapour was suffered to stagnate in the cavities where it is discharged. 



XLI. On the Variation of the Magnetic Needle ; with a Set of Tables exhi- 

 biting the Result of upwards of Fifty Thousand Observations, in Six Periodic 

 Revieivs, from the Year 1 700 to the Year 1756, both inclusive \ and adapted 

 to every Five Degrees of Latitude and Longitude in the More Frequented 

 Oceans. By fVilliam Mountaine and James Dodson, FF.R.S. p. 329. 

 Mr. M. and Mr. D. sometime before, by advertisements, announced their in- 

 tention of preparing a work of this kind ; and having, by application to many 

 corporate and public bodies, as the Commissioners of the Navy, the East India 

 Company, the Hudson's Bay Company, the Astronomer Royal, and numerous 

 commanders of ships, and other individuals ; by which means, having amassed 

 a vast number of observations of the variation of the magnetic needle, they 

 have here arranged them in very neat order in regular tables, as above announced 

 in the title of the paper, which might be of considerable use on many occasions. 

 Mr. M. and Mr. D. had formerly published some general charts, traversed by 

 many curve lines, showing the corresponding degrees of variation ; and on this 

 occasion they now present more complete and correct charts of the same kind, and 

 many curious remarks on this subject. 



