231 



to be in opposite electric states. The results of the experiments 

 tend to confirm the inferences of Matteucci. 



§ II. On the existence of Current Force in the Nervous Tissues. 

 After referring to the results obtained by Pacinotti, Puccinotti 

 Matteucci, and Du Bois Reymond, experiments are related in which 

 it is shown that if one electrode be inserted into the substance of the 

 brain, and the other be brought into contact with the blood flowing 

 from the internal jugular vein, an effect upon the needle occurs in- 

 dicating the blood to be positive ; an effect also was easily obtained 

 if the latter electrode was placed in contact with any other part of 

 the animal, such as the muscles. Reasoning from the results 

 obtained, combined with physiological evidence, it was considered 

 that they tend to establish the conclusion that the effects are due to 

 the changes which occur during the organic process of assimilation 

 or nutrition. 



4. On the Theory of Waves." By Andrevv John Robertson, 

 Esq. Communicated by the Rev. Henry Moseley, M.A., F.R.S. &c. 

 Received September 6, 1852. 



The author remarks that in the seventh volume of the Cambridge 

 Philosophical Transactions, Mr. Earnshaw has a paper on the Ma- 

 thematical Theory of the Waves of Translation, and that the objection 

 to the theory therein given has been pointed out by Professor Stokes 

 in a Report to the British Association, namely, that it requires a 

 mathematically sudden generation and destruction of motion. Pre- 

 viously to his having an opportunity of reading Mr. Earnshaw's 

 paper he had considered the subject in a manner entirely different 

 (Phil. Mag. Dec. 1850, March 1851). The analysis he then em- 

 ployed was not however such as to lead to results sufficiently general, 

 and he has in consequence now employed a higher analysis, in the 

 application of which he acknowledges himself indebted to Mr. Earn- 

 shaw's paper for considerable assistance. 



Taking the results deduced by Mr Scott Russell from his expe- 

 rimental inquiry, as the basis of his investigation, the author assumes, 

 — 1st, that the horizontal motion, produced by the passage of a 

 wave, in every particle of any vertical column is the same ; and 

 2nd, that the velocity of transmission is uniform. On these prin- 

 ciples he deduces the value of c, the velocity of transmission, 



in which h is the depth of the undisturbed water ; 2^ is the height of 

 a positive and the depth of a negative wave ; and g the accelerating 

 force of gravity. Hence it appears that the velocity is greater for a 

 positive than for a negative wave in the same channel. 



Comparing this result with Mr. Scott Russell's experiments, it 

 appears that on fourteen experiments of positive waves, the total 

 error is 3 j per cent, on the sum of all the velocities ; and that on 

 sixteen experiments of negative waves, the error is scarcely 2 per cent, 

 on the sum of all the velocities. The author infers that it may 



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