32 Dr. Reade on the permanent Soap Film, 



veloped before and beneath the level of the same part of 

 that body. 



The second, more extensive, intermediate between the 

 frontal and parietal eminences, is of a length proportioned 

 to the extent from before to behind of the corpus callosum. 

 It ceases behind on a level with the posterior margin of that 

 bod}\ 



The third section, often concave from above to below, some- 

 times even hollowed into a furrow on the median line, is pro- 

 portionate in length to that of that part of the hemispheres 

 completely separated, behind the corpus callosum. 



The fourth section, intermediate between the superior oc- 

 cipital protuberances and the upper curved line of the os 

 occipitis, displays in its middle a projecting quadrangle, 

 corresponding to the hinder extremities of the ventricles, and 

 to the convolutions situated behind and beneath these ex- 

 tremities *. 



March 30, 1840. 



V. Remarks on the permanent Soap Film and on Thin Plates, 

 By Joseph Reade, M.D. 



" Scilicet ut possem curvo dignoscere rectum, 

 Atque inter silvas Academi quasrere verum." — Horace. 



To the Editors of the Philosophical Magazine and Journal . 



Gentlemen, 



A S the entire of the second book of Newton's Optics is 

 -*■■*- based on the theory first advanced by Dr. Hook, or 

 rather by Mr. Boyle, " that colours are produced by the 

 thicknesses of the plates," supposing your scientific readers 

 well acquainted with that great philosopher's experiments, I 

 shall immediately proceed with my own. Should these be 

 capable of explanation according to the Newtonian theory, 

 I shall be ever ready to alter my opinions, and what at pre- 

 sent I conceive to be legitimate inferences. Aware of the 

 difficulties I have to encounter, and of the prejudices against 

 everything opposed to a doctrine stamped with the name of 

 Newton, and advocated by the most celebrated characters, I 

 hope for the indulgence of my scientific readers. 



Experiment 1. Having made a permanent soap film, as 

 already described in your Journal t> and shown two years ago 

 at the British Association at Liverpool, I placed the bottle 

 on an inclined plane on the table until all the bands of colours 



* An able report on the subject of Dr. Foville's researches has recently 

 been presented to the Academy of Sciences by Professor Blainville. It 

 contains further discoveries made by the Doctor with regard to the origin 

 of the eighth pair of nerves. 



t [Lond. and E4. Phil. Mag, vol, xi. p, 375,— Edit.] 



