Processes in the Useful Arts. 159 



an inch, so that four of them joined together make a complete circle. If 

 two bricks were placed with their thickest sides exactly opposite, the upper 

 and under surfaces of the two, when combined will be parallel, so that in 

 this way a cylindrical chimney will be formed, but when it is necessary to 

 bend the chimney, then two bricks are placed with their thick ends toge- 

 ther, and when it is required to bend it back again, the thin ends of the 

 bricks are placed on the same side as the thick ends were before. This will 

 be understood from Plate III. Fig. 4. Fig. 5 is a horizontal plan of the 

 flue. — See Newton's Journal, Aug. 1827, p. 325. 



8. Method of Mooring Ships in Roadsteads. By Lieut. Col. Miller, 



F.R. S. 

 The method of mooring ships proposed by Col. Miller, consists in secur- 

 ing a large buoy by means of a block of cast iron, so that it cannot be moved 

 by stress of weather, to which a vessel can make fast without letting go 

 her anchor. Col. Miller proposes to make the buoy of the following di- 

 mensions. 



Length, 16 feet. 



Diameter at middle, 9 



Do. at ends, 7^ 



Length of chain, 36 



Diameter of cast iron block, 3 



Do. at bottom, 5^ 



Height of do. 24 



Weight of do. 7 tons. 



The buoy must be bound with iron, and coppered, and a strong iron 

 hoop must pass round its centre, to which the chain and ring are attached. 

 --Ann, of Phil Aug. 1827, p. 110. 



9. On the adhesion of Screw Nails. By B. Be van, Esq. Civil Engineer. 



The screws used in these experiments were about two inches long — 



15 

 diameter at the exterior of the threads, — diameter at the bottom, the 



q t 



depth of the worm or thread being , and the number of threads in 



^ 1000 



h one inch 12. They were passed through pieces of wood exactly half an 



I inch in thickness, and drawn out by the weights given in the following 



table: 



Dry beech, 460 lbs. Dry mahogany, 770 lbs. 



Do. do. 790 Dry elm, 655 



Dry sound ash, 790 Dry sycamore, 830 



Dry oak, 760 



The force required to draw similar screws out of deal and the softer wood 



is about half the above.— PAi7. Mag. Oct. 1827, p. 291. 



