ADVERTISEMENT. 



from the Angular Pofition of Three known Obje6ls. 4. 

 Double Barrel and Winch for encreasing the Power without 

 Diminution of Strength. 5. Screw Press, which by the 

 contrary Action of Two Helical Threads, affords great In- 

 crease of Power at the Place of moft extreme Pressure. 6. 

 Pump acting by the Difference of Two Cylinders. 7. Al- 

 phabetical System of Writing in the Dark, by Mr. John 

 Gough. 8, 9. Two Plates, Apparatus for fupplying Worm- 

 Tubs, &c. with Water, on the Syphon Principle; By Sir 

 A. N. Edelcrantz. 10, 1 1. Construction of a fimple Repeater 

 for the Hours and Quarters, By Mr. J. M . Elliot. 1 2 . Diagram 

 to illustrate the Investigations of the Figure of the Earth> 

 by Professor Playfair. 13. Improved Chemical Furnace, by 

 R. Chenevix, Esq. F. R. S. 14. Figures to illustrate an 

 Improvement ip Spectacles, by W. H. Wollaston, M. D.. 

 F. R. S. 15. New Steam Digester, in which the Heat and 

 Pressure are rendered stationary ; by Sir A. N. Edelcrantz. 

 16. Remarkable Strata of Flint, by Sir Henry Charles Engle- 

 field, Bart. F. R. S. 17. Figure to illustrate Dr. Herschers 

 Theory of the Changes in the Situation of Double Stars. 1 8, 

 Mr. Hornblower*s Apparatus for fweeping Chimnies. 19. 

 Figures to explain the Changes of Double Stars, by Dr. 

 Herschel. 20. Galvanic Apparatus to afford the Maximuni 

 of Effect in Combustion, by I. R. I. 21. Hydraulic Engine 

 for raising Fresh Water, by the Discharge of Waste Water, 

 by Mr, Sharpies. 



Soho Square, Jprii, 1804, 



