338 An Astronomical Machine, the Tellurium. 



face, the outline being a logarithmic spiral. He found also that 

 certain portions of these might be cut off without diminishing 

 the effect. With respect to ascertaining the friction of the screw 

 on the water, great difficulty exists ; but he would refer to his 

 experiments, published some years ago in the Philosophical Trans- 

 actions, in which he measured the friction of the water against 

 a body revolving in it, by the time which a given weight took 

 to descend ; this body consisted of rings, and he found that the 

 friction or resistance through the water did not increase in propor- 

 tion to the number of rings. 



The following papers were also communicated. 



Report on railway constants, by Dr. Lardner. 



Remarks on the connexion which exists between improvements in pitwork and 

 the duty of steam-engines in Cornwall, by Mr. Enys. 



On Mr. Truscott's plan for reefing paddle-wheels, by Mr. Chatfield. 



On a plan of disengaging and reconnecting the paddle-wheels of steam-engines, 

 by Mr. J. Grantham. 



On a floating breakwater, by Capt. Taylor, R. N. 



Further report of the committee on the forms of vessels, by Mr. J. S. Russell. 



On an improved sight for rifles and other fire-arms, by Mr. C. T. Coathupe. 



On Capt. Couch's chock channels, by Mr. Snow Harris. 



On Arnott's stove, and the construction of descending flues, and their applica- 

 tion to the purposes of ventilation, by Mr. J. N. Hearder. 



Report of the committee on railway constants, by Mr. Edward Woods. 



On the granite quarries of Dartmoor, and their railways and machinery, by Mr. 

 W. Johnson. 



Report of the committee for applying a principle of Dynamometrlcal admeasure- 

 ment, invented by M. Poncelet, to the construction of a permanent indicator for 

 steam-engines. 



On a system of trussing for the roadways of suspension bridges, by Mr. Rendel. 



On the Plymouth breakwater, by Mr. Wm. Stuart. 



Art. XIV. — A?i Astronomical Machine, the Tellurium ; by 

 Edwin C. Leedom, M. D., of Plymouth, Penn. 



This is a machine for representing the motions of the earth 

 and moon. The earth, whose axis has its proper obliquity to the 

 ecliptic and keeps its parallelism, revolves round the sun in an 

 ellipsis similar to the natural orbit, and moves with such a velo- 

 city that an imaginary line joining the centres of these two bod- 

 ies, the latter being situated in one of the foci of the orbit of the 

 former, describes equal areas in equal times. The diurnal rota- 

 tions of the planet are also shown, each complete turn on its axis 



