1855.] 



ON THE COMPOSITION OF EGGS IN THE ANIMAL SERIES. 



301 



stone, Sir David Brewster ;* and a host of others. Under these 

 circuinstcinces we may be permitted to ask, why is it that two pic- 

 tures, taken by two cameras placed 2 J inches apart, do not show 

 sufficient stereoscopic relief? Why is it that we must place 

 the cameras about eight times farther apart than the human 

 eyes are in order to produce the proper relief? When these 

 questions first sugoested themselves to me, the following answer 

 occurred to me without at that time being able to prove it to 

 be the correct one ; namely, because the lenses in the oiimeras 

 (4 size) are twelve times larger than the human lenses (eyes). 



In order to ascertain whether this is the correct answer or 

 not, it was only necessary to take two pictures with two cameras 

 having a diaphragm in each, tjie openings in which are J of an 

 inch in diameter, that being the diameter of the diaphragm in 

 the human eye. In executing this experiment, I was very much 

 surprised to find that the focal range of the camera was in- 

 creased to an extraordinary extent. The cameras had been 

 focussed for a house on the opposite side of the street, but the 

 moment the diaphragm was introduced, the sash in the window, 

 which before was invisible, suddenly became as sharp and dis- 

 tinct as the house on which the focus had been previously 

 drawn. Subsequently, on removing the camera to an upper 

 story of my house, it was found that this increase in fiscal 

 range extended not only from the house towards the camera, 

 but to an equal extent beyond the house. After ascertaining 

 these facts, it became desirable to find out the cause of them. 

 With this end in view, the lenses were removed from the tube, 

 and only the diaphragm remained in the same. You may well 

 imagine my astonishment at finding the pictures of houses and 

 other objects in the street faithfully depicted upon the ground 

 glass ! the letters of signs, &c., reversed, precisely as if the 

 lenses had been used. The next step was to ascertain whether 

 these pictures possessed photogenic properties, which was soon 

 done by substitutiag a metal diaphragm with an aperture of 

 1-50 of an inch in diameter for the paper one of i inch in 

 diameter, putting in a coated plate, leaving it remain fifteen 

 minutes, coating it in the usual manner, and a beautiful 

 picture, similar to the one herewith sent, was the result. 



It was self-evident now, that we had the means to do that 

 with one camera, for which two were before deemed indispen- 

 sable, namely, taking two stereoscopic pictures through two 

 apertures situated only 2 J inches apart. But as a quarter size 

 plate is only 4.V inches long, and as it was desirable to take the 

 two pictures on one plate, two apertures 1-6G of an inch in 

 diameter were made in the metal plate above alluded to, only 

 2\- inches apart, and after twenty minutes exposure, the sun 

 shining on the house all the time, the accompanying pictures 

 were the result, thus demonstrating conclusively that two 

 stereoscopic pictures can be taken on one plate with one camera 

 (or dark chamber without lenses) and simultaneously, without 

 either reflectors or rcfractore of any kind whatsoever ! It may 

 here be remarked, however, that the pictures thus taken on one 

 plate are stereoscopic reverse, that is to say, the right picture 

 is on the side where the left one ought to be, and vice vo-Mt, 

 which can, however, be very readily remedied by cutting the 

 plate in two and pasting thcra together again properlj'. This 

 stereoscopic reverse was next attempted to be remedied by 

 placing a reflector before the apparatus, but the only eff'ect 

 produced by this device, was the same as the same- reflector 



* Mr. Maschcr disclaims, in the July number of the Journal of the 

 Frnnklin Institute, the merit of having first originateil the expliinutions 

 relating to the distortions of pictures. He refers to an article by Sir 

 David Brewster on that subject, published in vol. xv. Silliman's Jour- 

 nal, p. 291. 



produces upon pictures taken by an ordinary camera, namely, 

 making the pictures appear in their natural position, so that 

 letters on signs, ic, could be read correctly. 



There is another advantage resulting from this camera ; it 

 is this. You may make two, four, sis, or more sets of holes 

 in the same camera, either all of the same diameter, by which 

 means you will obtain an equal number of stereoscopic pictures 

 with the number of sets ot holes, or you may make one set 

 with apertures of 1-200 of an inch, another 1-100 of an inch, 

 one set 1-70 of an inch, and still another set with 1-25 of an 

 inch in diameter, where you will be certain to obtain at least 

 one set of pictures properly " timed," especially as the other 

 pictures which are not properly timed can be rubbed out before 

 gilding, thus saving the plates. 



On the Composition of Eggs in the Animal Series. 



while the eggs of Batrachia resemble those of the car- 



The conclusions to which M. M. Valenciennes and Fremy 

 have arrived with respect to the composition of Eggs in the 

 Animal Series are as follow : — 



C'onchisions. — We have shown, in three successive commu- 

 nications composing our memoir, the fiicts established by our 

 researches on the eggs of diiferent animals, belonging to all 

 the great classes of Ovipara. Let us by way of recapitulation, 

 endeavour to state in some general propo.sitions, the most im- 

 portant consequences which seem to be the results of this first 

 work. We have shown : — 



1st. That there exist fundamental differences between the 

 composition of the eggs of animals, and that under this col- 

 lective name of er/ff, designating the product of the ovarian 

 apparatus intended to contribute to the perpetuity of the species, 

 very diverse bodies are comprised, difi'erent as possible from one 

 another. 



2nd. That among the vertebrated animals, the eggs of birds, 

 of reptiles, and of fish, present in their composition, differences 

 which the simplest analysis cannot mistake, and besides that 

 the eggs of Sauria and Ophidia bear great analogy to those of 

 birds 

 tilaginous fishss. 



3rd. That the eggs of Arachnids and insects differ altogether, 

 as to their composition, from the eggs of other animals. 



4th. That those of Crustacea, organized for living in water, 

 do not at all resemble those of fish or of other amphibious 

 vcrtebrata. 



5th. That this extends to the eggs of Mollusks. 



Gth. That these differences correspond not only to classes or 

 orders ; that they extend to natural families even, without 

 stopping there, since we have proved that an egg of a cartilagi- 

 nous fish has not the same composition with that of an osseous 

 fish ; but further, that a Carp's egg is very different from a 

 Salmon's egg; that the egg of an Ophidian such as an adder's, 

 does not contain the same principles as those of the Cholunia. 



7th. That if the composition of diflerent proximate princi- 

 ples is the same in very nearly allied species, the form and the 

 size of vitellin granules vary in a manner sufliciently appreci- 

 able to be able to be recognised and assigned to each species. 



8th. That the albuminous substances furnished by eggs of 

 birds, reptiles, fish, crustaceans, present in their chemical pro- 

 perties and in their point of coagulation, differences which 

 permit us to suppose that these bodies are made up of diflerent 

 proximate principles. 



9th. That an egg changes its nature, — that its liquids alter 

 considerably at diflerent epochs of its formation, when detach- 



