MECHANICS AND USEFUL ARTS. 65 



Thus the grand object has been accomplished. In a few words, 

 M. Grimpe has succeeded in covering the two surfaces of the paper 

 (without changing- its nature) with a device which cannot be imitated 

 by hand, or transferred on to stone, and which can be printed with 

 ordinary ink. The commission conclude their report by stating, that 

 they have obtained undeniable proof that any stamp or device hitherto 

 known may be imitated, but for obvious reasons do not mention the 

 methods. Co?nptes Rendus, July 23. 



AMERICAN MICROSCOPES. 



MR. SPENCER, of Western New York, has hitherto been almost the 

 only person in this country who has turned his attention to the manu- 

 facture of microscopes, and he has succeeded in producing some instru- 

 ments of great power and excellence. Most of those, however, at 

 present in use in this country are of foreign construction. About a 

 year since, Mr. J. B. Allen, of Springfield, Mass., having had his at- 

 tention called to the subject of microscopes, with true Yankee perse- 

 verance and ingenuity, set about the construction of one of these in- 

 struments. Although he had never seen but one microscope, and 

 that only for a few minutes, and had never seen a piece of glass 

 ground, he devised his own tools and processes, and in the course of 

 a few months produced an instrument, which he exhibited to the 

 American Association, at Cambridge, in September. The power of 

 this instrument was about 1,300, and it received the most unqualified 

 commendation of the distinguished men there assembled. Professor 

 Agassiz, after a careful examination of it, made a report, in which he 

 spoke in the highest terms of its excellence. This instrument was 

 purchased by Amos Lawrence, Esq., of Boston, who liberally pre- 

 sented it to the academy at Groton, Mass. 



By the advice of Professor Agassiz, Mr. Allen immediately com- 

 menced the construction of another microscope, with some improve- 

 ments suggested by Professor A. This new instrument he completed 

 in about three months. It was submitted to the inspection of Profes- 

 sor Wyman, of Harvard University, who carefully compared it with 

 a similar microscope manufactured "by the celebrated Oberhauser, and 

 by him exhibited as one of his best instruments. The American 

 specimen was found to be fully equal, if not superior, to the Euro- 

 pean, and there can be no doubt that it is the most excellent micro- 

 scope ever produced in this country. 



It may not be improper to mention, that Mr. Clark, of Boston, has 

 succeeded in producing very fine telescopes, and that excellent chro- 

 nometers are now manufactured in this country. Thus it appears that 

 Americans have already made considerable progress in the manufacture of 

 these delicate instruments. Editors. 



THE SONOMETER. 



THE sonometer is a simple and easily-managed instrument, and con- 

 sists of a small bell fixed on a table. There is a pillar supporting a 

 serrated bar, and kept in its place by a delicate spring, to which a 



6* 



