PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 417 



American Institute Polytechnic Association, ) 



Jane ilh, 18G3. ) 



Chairman, S. D. Tillman, Esq.; Secretary, John W. Chambers. 



The subject for the evening, Mathematical Instruments, was opened by 

 the presentation of Blunt's Dividing Engine, for dividing mathematical 

 instruments, wlien the Cliairrnan said, 



This graduating engine i.s a very important instrument, for by it all 

 mathematical scales can be grailuutcd with great exactness, a feature of 

 immense value in all scientific measurements. We are indebted to the 

 improvements in mathematical instruments for those important discoveries 

 which have contributed so much to intellectual advancement in our age. 

 Th'e great diflerence between the ancients and the moderns, is that the 

 ancients discussed abstract questions only, without ever trying experi- 

 ments. This was the case in their study of Geometry, they failed to prac- 

 tically apply its laws, because they had no instruments with which to 

 make the necessary observations, and hence their progress was very slow 

 They reasoned by deduction alone. The.y were never precise in their state- 

 ments of physical facts, hence the inductive sciences were to them unknown. 

 It is related of Pythagoras that he sacrificed 100 oxen to the Muses, when 

 lie discovered that tlie square of the hypothenuse of a riglit-angled triant- 

 gle, is equal to the sum of the squares of the other two sides. Tlie appli- 

 cation of this problem in nKjdcr'n measurement, has led to very important 

 results. The mechanical ingenuity of very recent times has greatly facili- 

 tated the accumulation of the vast store of facts connected with the heav- 

 enly bodies. By the perfection of modern instruments we can more accu- 

 rately explore those portions of the universe within the range of human 

 observation. 



Among the instruments which have contributed to the advancement of 

 science, the telescope and microscope are the most prominent, for they 

 reveal to us innumerable wonders above and beneath. 



Thermometers. 



Mr. Victor Beaumont exhibited several specimens of his metallic ther- 

 mometers, and explained their mode of construction. They were made, he 

 said, of two strips of brass, with one of steel ; these three pieces were 

 bound together and placed in a fire, and soldered or brazed with silver. 

 These strips, after being brazed, vary more or less in their expansibility. 

 One will give a motion of one inch, and another three-fourths of an inch. 

 In graduating them they are placed in a room of fifty or sixty degrees 

 temperature, and are made to agree with the mercurial thermometer. They 

 have been some three years in use, and appear to give general satisfaction. 

 My object was to make a metallic thermometer that would be cheap in 

 comparison with the imported ones, and at the same time, accurate. Those 

 made at Paris and imported here, are sold at five dollars and upward, while 

 mine are made with improvements on the French, and sold at one dollar 

 and twenty-five cents, and one dollar and a half. 



Mr. Read. — What is the object in having the steel between the strips 

 of brass ? 



Mr. Beaumont. — The steel acts as a spring to bring back the brass when 



[Am. Inst.] B* 



