CONTENTS. scxi 



Tunnel beneath the Thames. — — — p. 473 



Abridged account of the plan and proceedings relating to the propofed tunnel beneath the Thames, 

 at Gravefend.— Lift of the committee of fubfcribers, with other particulars relating to the fub- 

 fcription. 



On Mr. Cartwright's Apparatus for rendering the piftons of Steam Engines 

 tight by Metallic Fittings. — — — P« 47^ 



February 1799. 



Engravings of the following Obje£l:s: i. A New Air-pump. 2. A remarkable 

 Lunar Halo : and, 3. Figures illuftrating the lateral Motions of Fluids. 



r. On the Corundum Stone from Afia. By the Right Hon. Charles Gre- 

 ville, F.R.S. _ _ _ p. 477 



Early notices of the corundum ftone. Particular account, and topographical remarks on the place 

 where it is ifound in India. It is in common ufe in China. Obfervations refpeAing its general 

 \ properties, fpecific gravity, &c. 



II. An Account of a Angular Flalo of the Moon. In a Letter from William 

 Hall, Efq. of Whitehall, to Sir James Hall, Bart. F.R.S. Edin. p. 485 



Lunar Halo, confifting of a circle round the moon of about la" in diameter, with another palling 

 through the moon of about i la*, and very much inclined to the horizon. 



III. Experimental Refearches concerning the Principle of the lateral Communica- 

 tion of Motion in Fluids, applied to the Explanation of various hydraulic Phe- 

 nomena. By Citizen J. B. Venturi, Profeffor of Experimental Philofophy at 

 Modena, Member of the Italian Society, of the Inftitute of Bologna, the Agra- 

 rian Society of Turin, &c. — — — P' 487 



A fudden bend, or right angle, in a pipe, deftroys nearly half the velocity of a fluid moving through 

 it. Enlargements are fcarcely lefs noxious. Explanation of the efFefts of the water-blowing 

 machine. ■ Curious method of draining land by a fall of water without machines, Caufes and 

 effefts of the eddies and whirls in rivers. 



IV. Concerning a new Variety of Argillaceous Iron-ore. By Samuel L. Mit- 

 qhill, M.D. uf New York. — — — p. 494 



Argillaceous iron-ore figured like bafaltes. Argument deduced in favour of the aqueous origin of 

 bafaltes. 



V. Concerning the Invention of the Eleftricai Doubler. By Mr. John 

 Read. — ' — , — P« 495 



Explanatory letter, with remarks on its contents. 



VI. Inquiries refpefting the Conftrudion of a Water-wheel, and the Manufadure 

 of Bricks. By a Correfpondent. — . — P- 497 



VII. On 



