Intelligence and Miscellaneous Articles. 305 



entitled " On Steady Motion in an Incompressible Viscous Fluid." 

 Dr. Oberbeck calls attention to the fact that in my paper the same 

 problem is proposed for solution that he investigated in vol. lxxxi. 

 of Crelle's Journal. I obtained the number of Crelle referred to, 

 and was struck by the similarity of the process in the latter part 

 of my paper, which relates to the motion of a sphere in the fluid, and 

 the method and results in Dr. Oberbeck's paper. For the method 

 adopted, however, a reference to page 349 of my article will show 

 that I did not claim absolute originality ; I merely amplified a 

 solution given by Mr. J. Gr. Butcher in vol viii. of the ' Proceed- 

 ings ' of the London Mathematical Society. The fact of having 

 of necessity employed the methods of spherical harmonics, and also 

 of having employed Borchardt's theorem, produces the only resem- 

 blance that exists in the two papers. As to Borchardt's theorem, I 

 can merely say that I have used it a dozen times since I first became 

 acquainted with it, in the winter of 1876, while attending a course 

 of lectures on electricity in the Johns Hopkins University. I have 

 used the theorem in three different papers on the motion of viscous 

 fluids. 



Dr. Oberbeck states that we propose the same problem. This 

 does not appear to be the case, as a comparison of equations (4) of 

 my article with his equations of motion will show. Dr. Oberbeck 

 limits his problem to the case of very small velocities, such that 

 the products of the velocities and their differential coefficients can 

 be neglected. Such a restriction obviously does not obtain in my 

 paper. The problem which I have proposed, therefore, and of which 

 I have offered & possible solution, is much more general than that 

 proposed by Dr. Oberbeck, and for which he obtains an exact 

 solution. The vanishing of v 2 £, v 2 *?> V 2 £ has an entirely different 

 significance in the two papers. In the form of the expressions 

 obtained for the velocities in the case of a moving sphere, I cheer- 

 fully accord the priority to Dr. Oberbeck, though (from the different 

 natures of the two problems) the quantities entering into these 

 expressions do not have the same significance. I have only to say 

 in conclusion that I have never seen Dr. Oberbeck's paper before 

 today. 



Hoping, gentlemen, that you may find it convenient to give this 

 letter an early insertion in the Philosophical Magazine, 



I remain, yours very respectfully, 



Thomas Cbaig. 



DETERMINATION OF THE FUNDAMENTAL COLOUR- SENSATIONS BY 

 THE STUDY OF THE DISTRIBUTION OF THE COMPLEMENTARY 

 COLOURS IN THE CHROMATIC CIRCLE. (SECOND NOTE.) BY 

 M. A. ROSENSTIEHL. 



1. In studying the distribution of the red, yellow, green, and 

 blue in the chromatic circle, I have found that there are in that 

 circle three colours "which, in relation to our eye, possess special 



