1892.] President's Address. 313 



show important variations from Bouvard's work, which variations in 

 their important particulars were confirmed by Dr. Hartwig. 



Next (1885) the relative motions of the Pleiades were taken up 

 with a view of tracing gravitational effects in the various members 

 of the group. This question is not ripe for solving, but it induced 

 heliometer observers to take up the question, and important progress 

 is now being made. 



The photometric work detailed in the ' Uranometria Nova Oxon- 

 iensis,' also published in 1885, consisted in measuring the light 

 received from all stars visible to the naked eye, to 10 south de- 

 clination, by means of a wedge photometer devised by Professor 

 Pritchard a form of photometer now in the hands of many astrono- 

 mers. In the course of this work Professor Pritchard, at his own 

 expense, took an assistant to Egypt to determine the effects of atmo- 

 spheric absorption in a more constant climate than that of Oxford. 

 This photometric work has been recognised by the award of the Gold 

 Medal of the Royal Astronomical Society. 



Having fully determined the capacity of photography for accurate 

 measurement, Professor Pritchard next applied it to parallax deter- 

 minations of stars of the second magnitude. Some thirty stars 

 altogether have been investigated, and this work is now in the press. 

 Thirty is a greater number than any other astronomer has attempted. 



Professor Pritchard is now working on the International Chart of 

 the Heavens, and taking part in researches to ensure an accurate 

 photometric scale. 



ROYAL MEDAL. 

 John Newport Langley, F.R.S. 



Some of the most important of Mr. Langley's researches have been 

 upon the Physiology and Histology of Secreting Glands. Extending 

 the observations of Kiihne and Lea on the pancreas, Mr. Langley 

 showed in an elaborate series of researches, extending over the sali- 

 vary and most of the important secreting glands of the body, that 

 the formation, as a morphological element within the secreting cell, 

 at the expense of its protoplasm, of the material to be used in the 

 secretion is a general function of secreting cells. The dependence of 

 this function upon the activity of nerves, and upon other forms of 

 excitation, such as the action of drugs, has been greatly elucidated in 

 the course of these researches. Concurrently with the morphological 

 changes within the cells, the chemical changes which occur within 

 the secretion as the result of nerve activity or inactivity have been 

 investigated, and many important facts brought to light regarding 

 the nature of the action or modifications of the action which may be 

 brcught to bear upon the secreting cell through the nervous system. 



