220 Mr. E. H. Griffiths. Determination of Boiling [June 19 y 



show the line at X 500 first observed in a comet by Dr. Huggins in 

 the year 1866. It remains for those who hold that the physical 

 structure and temperature of comets and nebulae are not similar in 

 each case to explain the phenomena observed in a more simple and 

 sufficient way. 



June 19, 1890. 

 Mr. JOHN" EVAN'S, D.C.L., LL.D., Treasurer, in the Chair. 



The Rev. J. Kerr, Prof. W. H. Perkin, jun., Mr. D. Sharp, and' 

 Mr. W. F. R. Weldon were admitted into the Society. 



The Presents received were laid on the table, and thanks ordered for 

 them. 



The following Papers were read : 



I. " On the Determination of some Boiling and Freezing 

 Points by means of the Platinum Thermometer." By 

 E. H. GRIFFITHS, M.A., Sidney Sussex College, Cambridge. 

 Communicated by R. T. GLAZEBROOK, F.R.S. Received 

 May 27, 1890. 



(Abstract.) 



The paper contains an account of experiments made with a view 

 of 



(I.) Comparing the closeness of agreement between the readings 

 of platinum thermometers made from different samples of wire 

 arranged in different manners and insulated by different materials. 



(II.) Ascertaining some accurate method of graduating such ther- 

 mometers without the direct use of the air thermometer. 



(III.) The determination of certain boiling and freezing points. 



Eight thermometers were constructed. The resistance of the 

 platinum coils used varied from about 4 to 50 ohms. Full particulars 

 of these thermometers are given in the paper. 



The insulating substance in thermometers A, B, C, D was glass 

 only ; but the internal arrangements were different, as also were the 

 samples of platinum wire used in their construction. 



The form finally adopted (that of E, F, G) was as follows: A 

 coil of fine platinum wire was wound on a roil of asbestos paper and 

 slipped into a thin hard-glass tube. Thick platinum wires ran from 



