Nov. 3. 1855.] 



NOTES AND QUERIES. 



351 



his support. Evelyn, under date of Dee. 13., 

 which was on a Thursday, says " the king flies to 

 sea ; " though in fact James fled at three o'clock 

 in the morning of Tuesday, the 11th, from 

 London, and his flight was arrested on Thursday 

 the 13th. The destruction of the new Catholic 

 chapels in the metropolis took place on the nijjht 

 of the 11th, and the example was followed by 

 similar outrages throughout the country. The 

 second flight of James was on Tuesday the 18th, 

 and his final embarkation at the dawn of Sunday 

 the 23rd. The Running Thursday was most 

 probably Thursday the ISth, when the news of 

 his first flight became generally known. 



If this answer be somewhat of a guess, I must 

 confess that its purpose is to introduce with it a 

 Query. K. T. alludes to a manuscript at Broms- 

 grove which gives " an account of his family." 

 From the extract quoted, and the initials of the 

 querist, I conceive the family to be that of Throck- 

 morton. I have an interest in the Throckmortons 

 of the seventeenth century from ancestral con- 

 nexion. Would R. T. Inform me if the manu- 

 script gives any account of Sir Francis Throck- 

 morton, who died 1680, and Ann his wife, 

 especially the latter, who lived to a great age, not 

 dying till 1724 ? Might I also inquire in whose 

 possession the manuscript rests ? Monson. 



Gatton Park, 



PHOTOGRAPHIC CORRESPONDENCE. 



Single Stereoscopic Pictures. — My sliort comment upon 

 this subjept (Vol. xii., p. 273.) having induced some far- 

 ther remarks from Mk. Thos. Rosk and Ma. Ixgleby 

 (Vol. xii., p. 333.), which appear to call for additional 

 explanation from me, I beg to offer the following. The 

 photograph as proposed to be taken by Mk. Norman 

 (Vol. xii., p. 171.) is produced virtually by two lenses 

 having their foci coincident, or, what is the same thing, 

 by malting use of two parts of one lense by means of two 

 small apertures near the circumference, the apertures 

 being 2^ inches apart. The consequence of this arrange- 

 ment is, that objects in the same plane in the principal 

 anterior focus of the lens would be depicted sharply and 

 clearly, while those in planes more remote would present 

 a somewhat obscured outline, owing to their being de- 

 picted from a different point of view by the two lenses; 

 the bearings (to use a nautical phrase) of the proximate 

 and distant objects varying from one another, according 

 to the spot whence observed ; lience the impression upon 

 the mind, when a picture resulting from Mr. Nouman's 

 arrangement is viewed by means of one eye, is very 

 similar to that produced by viewing solid objects with 

 both eyes. The distance between the points of view being 

 smaller than Mr. Rose considers useful, is only a question 

 of degree, not of fact. Mr. Rose has attributed to me 

 observations regarding increased intensity, which should 

 have been applied elsewhere. 



My observation that all parts of a single picture are 

 equally distant from the observer, is of course only approxi- 

 mately true, the same applies to the usual two pictures ; 

 but in one case this fact would be discoverable in con- 

 sequence of the uniform convergence of the axes of both 

 eyes, if brought to bear upon all parts of the picture, 



No. 314.] 



whereas with two pictures this is not the case, each ej'e 

 being confined to its own picture alone. Geo. Shadbolt, 



I am pleased to find that my communication has 

 caused some discussion from several gentlemen, who have 

 not thought it necessary to adopt language tending to 

 throw ridicule over the matter. 



In one point I beg, however, to suggest to Mr. Rose 

 that he is not quite correct, when he states that no 

 stereoscopic effect can be produced at such a small angle, 

 but onlj' an intense picture formed by the superposition 

 of two pictures exactly alike. 



Now it appears to me that if the two diaphragms be 

 2^ inches apart, surely the two pictures must differ to 

 the same extent as the two pictures produced on the 

 retinae of the eyes (the same distance apart). 



I mentioned in my first communication that such an 

 angle was far too small to produce the ordinary exag- 

 gerated stereoscopic effect ; but that a pair of lenses 

 placed some distance apart (but still superimposing the 

 two pictures on the screen) would in all probability pro- 

 duce everj'thing to be desired. 



I shall be glad to learn that some gentleman, having 

 the necessary time and means at his disposal, will try the 

 experiment fairly, and give the result, which, if I mistake 

 not, will be important. George Norman. 



Hull. 



The Stereoscopic Question. — I observe, in your recent 

 Numbers, a dispute on the theory of the stereoscope, in 

 which Mr. Norman, Mr. Ingleby, Mr. Rose, and Mr. 

 Shadbolt have taken a part. As there cannot be two 

 opinions on a question of pure science, it is not difficult 

 to settle the points at issue between these gentlemen. 



Mr. Norman is mistaken in supposing that the photo- 

 graphs taken by his altered camera have a stereoscopic 

 effect different from that produced by every other photo- 

 graph. He is correct, however, in stating that the pho- 

 tographs produced by his altered camera have, when seen 

 with one eye, a good stereoscopic effect. The writer of 

 this Note published and explained this fact long ago, and 

 has shown it to many persons. The effect is finely seen 

 in a large photograph of a bust, or of a street much fore- 

 shortened. In these the stereoscopic effect is perfect. 



The imperfect stereoscopic effect of the best executed 

 portrait, or building, or landscape, upon a plane surface, 

 when seen by both eyes, is that we learn, from the slight 

 change in the convergency of the optic axis while sur- 

 veying the picture ; that all the parts of it are nearly 

 equidistant from the eye, and are therefore painted upon 

 a plane surface. Wheieas, when we view the same ob- 

 ject with one ej-e, we lose the power of estimating dis- 

 tance given us by binocular vision ; so that the lights 

 and shadows, and" the ajrial or geometrical perspective, 

 are allowed to produce their full effect. Mr. Shadbolt 

 has stated this more briefly, but correctly. 



The eye may, by a little practice, be taught to see a 

 perfect stereoscopic picture by simple vision ; but the 

 effect is instantaneously produced when both eyes are 

 good, and equally so either by squinting or by a stereo- 

 scope. The true theory of the stereoscope was first given 

 by Sir David Brewster, in the Transactions of the Royal 

 Society of Edinburgh, some years ago; and his paper was, 

 we believe, reprinted in the Philosophical Magazine. 

 Persons unacquainted with the true theory of binocular 

 vision, upon wliich the theory of the stereoscope is 

 founded, are attempting to produce stereoscopic effects by 

 the union, upon a plane surface, of the two dissimilar 

 images of solids ; but they may rest assured that the 

 attempt will be fruitless. M. N. 



