pient, through the bounty of Mr. Henry Shaw, of the valuable historical 

 library of the late Bishop Robertson. 



Believing that the establishment of such a source of information is a* 

 solid gain to the cause of culture in our midst, we take occasion, on be- 

 half of the interests that our Society represents, to tender to Mr. Shaw our 

 thaniis for his generous donation to our Associate Society. 



On motion, the resolution was adopted by the Academy, and 

 the Recording Secretary instructed to send a copy to Mr. Henry 

 Shaw. 



Mr. J. H. Kinealy demonstrated how to derive Rankins' Ex- 

 pression for the Thermo-dynamic function in terms of the tem- 

 perature and pressure (given in The Steam Engine^ p. 314) on 

 the supposition that the formula represented only perfect gases. 



Prof. Nipher read a jDaperon ''The Regulation of the Dynamo," 

 which was referred to the Committee on Publication. 



Fchrtiary 215/, 1887. 



President Nipher in the chair ; nine members present. 



Dr. Liideking exhibited an apparatus for determining the iron 

 in the atmospheric air. It consisted essentially of a Marriotte's 

 bottle, having a Liebig's potash bulb apparatus attached to the 

 air-tube. By this means known volumes of air were made to pass 

 quite gently and regularly through the bulbs filled with hydro- 

 chloric acid as an absorbent. The iron was then determined in the 

 fluid of the bulb apparatus colorimetrically by means of sulpho- 

 cyanide of potassium. 



The quantity of iron in a cubic foot of air was found to vary 

 within the limits of 0.000003 and 0.000026 grammes in six experi- 

 ments made in the month of February, which results are quite in 

 accordance with those of Tissandier, obtained in Paris by an en- 

 tirely different mode. The experiments will be continued through 

 the year and the results presented to the Academy. In day-time 

 the iron was present perhaps in ferrous state and during the night- 

 time in ferric state. 



Dr. Liideking was requested to write out a description of his 

 experiments with their results, and present the same to the Acad- 

 emy for publication. 



