Royal Society. 385 



tion of the vitellus from evaporation, but not its coagulation, an 

 effect even not produced by steam of the same temperature, but 

 which is occasioned by boiling in water, owing, it is inferred, to an 

 admixture of water. 3rdly, on the action of alkalies and salts ; how 

 these, such as potassa, ammonia and their sesquicarbonates in solu- 

 tion, nitre, acetate of lead, common salt and others, when of 

 moderate strength, not only do not coagulate the vitellus, but have 

 the property of dissolving a certain portion of coagulum, and coagu- 

 late it only when very much diluted. 4thly, on the action of acids 

 and some other agents ; how the vegetable acids tried, as the tar- 

 taric, oxalic, acetic, whether strong or dilute, do not coagulate the 

 vitelline fluid, but dissolve its coagulum ; how the strong sulphuric 

 and muriatic acids inspissate it, the weak coagulating it ; and fur- 

 ther, how it is coagulated by the nitric acid, by corrosive subhmate 

 and by alcohol, but not by iodine. 



The inference from the experiments drawn by the author is, that 

 the vitellus of the Charr and of the eggs of the other Salmonidse is 

 distinct in its properties, both from the albumen and yolk of the eggs 

 of birds. He conjectures from analogy that the ova of other species 

 of osseous fishes will be found to be similar; but not so those of the 

 cartilaginous fishes. According to the observations he has made, the 

 yolk of the eggs of fishes of this order, whether they possess a white, 

 as in the instance of the oviparous ; or are destitute of a white, as in 

 that of the viviparous, resembles in its general character that of the 

 egg of birds : but he doubts that the white of the former will be 

 found analogous to that of the albumen ovi of birds, at least in its 

 chemical qualities ; having in one instance, that of the egg of the 

 Squalus Catulus, found it to be, whilst transparent and viscid, neither 

 coagulated by heat nor by nitric acid. 



In conclusion, he suggests that the coagulation of the ova of the 

 Salmonidae may have its use, inasmuch as the opaque white ova are 

 more conspicuous than the transparent, — the dead than the living, — 

 and in consequence, the one may serve as lures and divert from the 

 others the many enemies to whom they are attractive food. 



Feb. 12. — The following communications were read: — 



1. The subjoined Letter from Professor Haidinger to Captain 

 Smyth, R.N., For. Sec. R.S., dated Vienna, January 15, 1852. 



Sir, — The great success with which optical i - esearches are treated 

 of in the publications of the Royal Society, must make me anxious 

 to lay before the Society, in a few words, a concise and convincing 

 demonstration of the theorem that in a ray of polarized light the 

 vibrations are perpendicular to the plane of polarization, conform- 

 ably to the views of MM. Fresnel and Cauchy, and not in the plane 

 of polarization, as some other mathematicians have maintained. 



My demonstration is founded on the nature of dichroitic crystals, 

 as tourmaline, sapphire, idocrase, &c. Any perfectly homogeneous 

 crystal of this description presents two different tints of colours. 

 One of them appears in the direction of the axis, as well as in all 

 directions perpendicular to it, and it is always polarized in a plane 



Phil. May. S. 4. Vol. 3. No. 19. May 1852. 2 C 



