' Hydraulic Experments.-^Art tf Printing. 6r 



III. p. t6. — The excitation of tound in organ-pipes is efFe£led by this communication. Ihld. 

 The fame caufe augments the force of found in conical divergent pipes. Ibld.T^. 17. ^Re- 

 markable differences between the refonant vibrations of the air in a pipe, and the pulfations 

 propagated in die atmofphere. Ibid. 



The contraction of the fluid vein which tflues through a thin plate, is not the Newtonian 

 cataraft. III. p. 18 — The velocity of the contrafled flream through a thin plate is nearly the 

 fame as that of a heavy body which may have fallen through the height of the charge. III. p. 19. 

 , — Singular form of the ftream which is emitted through a lonjr hole or cleft. Exper. 31. III. 

 p. 20. — In right-lined orifices the fides of the contra£ted ftream anfwer to the angles of the 

 orifice, and the contrary. Caufe of this phenomenon. Ihid. — The contradion of the fluid 

 vein is made at a greater diftance under aftrong charge than when the charge is weak> Exper. 

 32. III. p. 21. — Other varieties in the figure and velocity of the contracted ftream. Exper. 33 

 and 34. Ibid. — Expenditure through a tube, the inner extremity of which is thruft into 

 the cavity of the refervoir itfelf. Exper. 35. Ibid. 



V. 



A Memoir on the Typographic Art, by Alexis Rachon, of the French National Injlitute, and 

 Dlredor of the Marine Obfervatory at the Port of Brejl. 



A YPOGRAPHY is the art of multiplying copies. Amongft the procefTes to which the 

 improvement of this art has given rife, there is one for ever memorable in the records of 

 fcience and of art. This fimple defignation is fiifficient to point out the invention of printing;, 

 and the reader will be ready to obferve, that it is unnecefiary to defcribe the utility of this 

 happy expedient, the fruitful and inexhauftible fource of mental illumination, the ever-durable 

 regifter of all nations. Men of information well know, that the notions acquired by readino- 

 conliitute the bafis of all our fcience; and it is to the art of printing that we are moft indebted' 

 for thefe acquifitions. 



Henceforth the precious depofit of our fciences and arts is preferved, and nothing fliort of 

 univerfal convulfion can deftroy it. This wonderful art gives to man the faculty of tranfmitting . 

 the refult of his enquiries to his fellow men> however difperfed over the furface of the globe, or 

 even though removed to thofe periods of duration which fhall be occupied by our remoteft" 

 pofterity. If this precious invention had been known to the ancients, we furely fliould not: 

 have to regret, at this moment, the numerous mafter-pieces of compofition, and the many 

 ufeful arts which time has for ever covered with obfcurity. 



Let thofe who fliew an ignorant contempt for the mechanic arts, diredl their attention to 

 this, and repent their errors. Let them renounce thofe unhappy prejudices which tend to dif- 

 Gourage the numerous and refpeCtable clafs of induftrious artifts. Much fagacity has certainly 

 been required to carry our arts to the degree of perfection they at prefent poiTefs. I will fay 

 mote, and bring the art of printing in fupport of my aflertion. — One fingle happy difcovery 



is 



