Froceebings of the Polytechnic Assoctatwn. 857 



the useful arts. He concluded by saying he should always feel a 

 deep interest in the future success of the gentlemen who had done 

 so » much to advance the interests of this branch of the American 

 Institute. 



The Association then adjourned to meet on the second Tliursday 

 of October next. 



October 14, 1869. 



Samuel D. Tillman, LL. D., in the chair: C. E. Emery, Esq., Secretary. 



The Chairman, after welcoming the members to their accustomed 

 places at the first fall meeting, presented the following scientific 

 memoranda : 



Kew Colok Test foe Blood. 

 The London Lancet states, on the authority of. Prof. Bloxam, of 

 King's College, that a mixture of tincture of guaiacum and a solution 

 of peroxyd of hydrogen in ether instantly produces with blood or 

 blood-stains a beautiful blue tint. He had extracted a single linen 

 fiber in the sample of a blood-stain twenty-years old, and with an 

 almost inappreciable amount of stain on it ; and he found the charac- 

 teristic blue color was immediately induced by the test, and readily 

 detected by microscopical examination. 



Pocket Spectroscope. 

 The new optical glass of great density, made by Messrs. Chance of 

 London, has been used for four of the ten prisms contained in a 

 direct vision spectroscope, which is small enough to be carried in the 

 pocket, yet so powerful that it shows the D lines of the spectrum 

 widely separated. ' 



Singular Molecular Change. 

 While making some experiments on lieating strained iron wire to 

 redness, by means of electricity, Mr. Gore observed that after discom- 

 necting tlie battery, and during the process of cooling, the wire sud- 

 denly elongated, and then gradually shortened until quite cold. A 

 number of experiments were made with wires of different metals and 

 alloys, but in no otlier case was a similar change detected. The 

 amount of elongation in the iron wire was found to be about l-240th 

 part of its length. During the process of heating the wire, no 



