650 [June 18, 



In order to show that the sensitive paper, when exposed to ordi- 

 nary sunlight, becomes homogeneously tinted, the author appends 

 the readings, taken in the way described, from various portions of a 

 piece of the standard paper used for the sun-pictures exposed for 

 some seconds to direct sunlight. 



Reading. Deviation from mean. 



Portion -No. 1 .. 101-4 + 0-93 



2 .. 1007 +0-23 



3 .. 98-5 .... -1-97 

 4 .. 101*6 +1-13 



5 .. 99'9 .... -0-57 



6 .. 100-7 +0-23 



Mean.. 100*47 



The sun-pictures obtained on the sensitive paper must possess 

 only a slight tint, otherwise the differences in shade cannot be 

 accurately observed ; they then exhibit a peculiar coarse mottled 

 appearance, which is not due to imperfections in the paper or the 

 lenses, nor to the action of the earth's atmosphere. 



Perhaps these irregular dark and light patches are owing to clouds 

 in the solar atmosphere, and they may have an intimate connexion 

 with the well-known phenomenon of the red prominences. 



Mr. Baxendell and the author propose to carry out, according to 

 this method, a regular series of observations of the variation of the 

 relative amounts of brightness on the sun's disc, and they hope be- 

 fore long to be able to present the Society with some further details. 



X. "On the Contractility of Healthy and Paralysed Muscles as 

 tested by Electricity." By HARRY LOBB, Esq. Com- 

 municated by JOHN SIMON, Esq. Received April 30, 

 1863. 



If a moist conductor from the positive pole of the finer wire of an 

 electro-magnetic battery* be placed upon the skin covering the origin 

 of a healthy muscle, and the moist conductor from the negative pole, 

 upon its belly, and a current of moderate intensity be allowed to pass, 



* The apparatus used in these experiments is the small portable machine of 

 M. Duchenne, made by Charriere. 



