Mr. Wheatstone on Resonance. 183 



in the intensity of the sound ; this effect is called beating, and the 

 o-reater the deviation irom unison is, the more rapid are the beats. 

 From what has been above stated, the same column of air may 

 reciprocate sounds differing in pitch ; if, therefore, two vibrating 

 tuning-forks, imperfect unisons to each other, be brought together 

 over the embouchure of a flute, or the open end of a tube containing 

 an appropriate column of air, the periodical recurrence of the beats 

 will be rendered strikingly evident, slowly or rapidly succeeding 

 each other, accordingly as the forks are more or less in tune with 

 each other. 



On the recent Improvements in the Art of Printing, 



[Communicated by Mb. Cowper,] 

 It is a remarkable fact, that from the invention of the art of printing, 

 to the year 1798, a period of nearly 350 years, no improvement had 

 been introduced in this important art. In Dr. Dibdin's interesting 

 account of printing, in the Bibliographical Decameron, may be 

 seen representations of the early printing presses, which exactly 

 resemble the wooden presses in use at the present day. — The im- 

 mense superiority of the press over the pen induced, perhaps, a 

 general belief that nothing more was possible, or it might be that 

 the powers of the press were quite equal to the demand for its 

 productions. 



A new era has, however, arisen, the prompt and extensive cir- 

 culation of the public journals and other periodicals requiring 

 powers which the ordinary press could never reach. 



The first important improvement of the common press was the 

 invention of the late Lord Stanhope. This press is composed 

 entirely of iron ; the table, on which the types rest, and the platten, 

 (or surface which gives the impression,) are made perfectly level; 

 he has thus introduced better materials and better workmanship, 

 to which, however, he added a beautiful combination of levers, 

 to give motion to the screw, causing the platten to descend with de- 

 creasing rapidity, and consequently with increasing force, till it 

 reaches the type, when a very great power is obtained. There 

 have been, perhaps, twenty contrivances for obtaining the same 

 effect ; but as a press. Lord Stanhope's invention has not been sur- 

 passed. Still it is only a press, and in point of expedition has 

 little superiority over its wooden rival, producing 250 impressions 

 per hour. 



Jjord Stanhope was also the successful reviver of the art ofs\^ 



