S0§ Royal Society. 



over the same meridians. The difference of these times gives the dif- 

 ference of longitude independent of the right ascension of the stars. 

 Both observers then reversed the axis of their transit instruments ; 

 Cambridge selected a second pair of stars from the list, and the same 

 series of observations was repeated as with the first pair. The error 

 of coUimation was thus eliminated, and by confining the observations 

 to stars within about five degrees of the zenith, the influence of azi- 

 muthal error was avoided. The level being reail at every reversal, 

 the correction for it was applied by computation. In this manner 

 it is hoped to eliminate every possible source of error, except that 

 which arises from the personal habits of the observers. In order to 

 eliminate this error, a travelling observer worked for a time at Cam- 

 bridge and compared with the Cambridge astronomer; then came 

 to New York and compared with the New York astronomer ; then 

 returned to Cambridge again, and so on as often as was thought 

 necessary. Finally, at the conclusion of the campaign all the ob- 

 servers were to meet at Cambridge and make a general comparison 

 of their modes of observation. 



On one or two nights the preceding programme was changed, and 

 each observer telegraphed both star A and star B. 



"On the peculiar cooling effects of Hydrogen and its com- 

 pounds in cases of Voltaic Ignition." By W. F. Stevenson, Esq., 

 F.R.S. 



In this communication the author gives several theorems which 

 he considers to be established by the experiments cited in a pam- 

 phlet which he published, entitled " The Non-decomposition of Water 

 distinctly proved." He then states, that when we apply the prin- 

 ciple of these theorems to Mr. Grove's discovery of the cooling 

 properties of hydrogen, it will be found to admit of a most simple 

 solution : " for instance, when the coil of platinum wire is connected 

 with the poles of the electric battery, and the current is established, 

 it is evident that the electric matter thus passed through the wire 

 must escape at the contrary end (the air with which the wire is 

 surrounded not being a conductor of electricity), and as the quan- 

 tity of electric matter thus transmitted is considerable, and its exit 

 from the wire confined but rapid, that commotion before noticed 

 (in one of the author's theorems) necessarily ensues and causes the 

 ignition of the wire ; but when the coil of wire is immersed in 

 hydrogen, which is a conductor of electricity, it is evident that the 

 electric matter must be, at the same moment, abstracted or con- 

 ducted from every portion of the wire, and consequently the com- 

 motion or rush of the electric matter at the extremity of the wire, 

 which causes the ignition, is suspended and the comparative cool- 

 ness of the wire is the necessary result." 



Postscript to a paper " On the Ganglia and Nerves of the 

 Heart," with two drawings. By Robert Lee, M.D., F.R.S. 



The author states that since his former communication Avas pre- 

 sented to the Royal Society he has made a very minute dissection 

 in alcohol of the whole nervous system of the young heifer's heart. 



