March g, 1888.] 



SCIENCE. 



119 



with black crystals attached, and grinding it with a polished sapphire, 

 it readily scratched the same. If a larger quantity of material 

 comes to hand, the writer will have polished a diamond with the 

 powder of the meteorite, using a new wheel for the purpose. The 

 writer has not seen the paper of MM. Latchinoff and Jorefeif, but 

 there seems to be every reason to substantiate their conclusions. 



These facts are of especial interest, since on Jan. 15, 1887, Prof. 

 L. Fletcher, curator of the Mineralogical Department of the British 

 Museum, read before the Mineralogical Society of England a paper 

 on a meteorite which was found in the sub-district of Youndegin, 

 Australia, in 1884, and in which he stated he had found a new 

 form of graphite of cubic form, with the hardness of 2.5 and a 

 specific gravity of 2.12. To this he gave the name of ' cliftonite,' 

 calling attention, also, to the fact that Haidinger, in 1846, had found 

 what he described as graphite pseudomorph after iron pyrites 

 {.Pogge7idorf AiDiakn, 1846, l.xvii. p. 437), obtained by him from a 

 nodule of graphite which had dropped out of the Arva meteorite. 

 Gustav Rose ( Beschreibung tend Entheilimg der Meteoriien, 

 1864, p. 40; Poggendorf Annalen, 1873) expressed an opinion that 

 this mode of replacement of the cube edges on these crystals was 

 suggestive of holo-symmetry rather than hemi-symmetry, and that 

 this interpretation would exclude iron pyrites as a possible antece- 

 dent mineral. 



The cliftonite was readily examined with a J-inch objective ; and 

 from its structure Professor Fletcher concluded, that, while it is dif- 

 ferent from native graphite, the sharpness, separateness, and com- 

 pleteness of the crystal, the brightness of the faces, the delicacy of 

 the acicular projections, and especially of the obtuse, almost flat, 

 square pyramids, or some of the faces, are quite sufficient to prove 

 that the form has never had any other than its present tenants ; in 

 other words, ihat it is not a pseudomorph. When in cubes, the 

 diamond has faces not very unlike those of the Youndegin crystals, 

 and shows a similar bevelling of its edges by the rounded tetrahex- 

 edra. Again : Professor Fletcher says it might be argued, that, 

 during a hurried crystallization of the carbon, circumstances initial- 

 ly favorable to the formation of the diamond had finally permitted 

 the existence of carbon in a graphitic form only. He had also 

 found distinct graphitic crystals, cube octahedrous in form, in the 

 Cocke and Sevier County (Tenn.) meteorites. 



When we consider that only a few meteorites have been exam- 

 ined for this mineral, we have reason to expect some interesting 

 results in the future. George F. Kunz. 



New York, March 6. 



A Pseudo-Meteorite. 



Through the kindness of Dr. DeWitt Webb of St. Augustine, 

 Fla., I have been able to examine a portion of the so-called ' meteor- 

 ic stone,' weighing over two hundred pounds, which was said to 

 have been seen to fall in an old cultivated field near Middleburgh, 

 Clay County, Fla., and which was exhibited at the Subtropical Ex- 

 position at Jacksonville, Fla. It is a concretionary limonite, and 

 not of meteoric origin. George F. Kunz. 



New York, March 6. 



Monocular vs. Binocular Vision. 



As a constant student of binocular phenomena, I have been 

 much interested in Mr. Hyslop's letter in Science of Feb. lo. I 

 have repeated the experiment illustrated by his Fig. i, and con- 

 firmed his results. But I do not think they are to be explained by 

 any supposed struggle between monocular and binocular vision, 

 but in a far more obvious way, which, in fact, he himself suggests. 



In binocular combination of such simple figures as circles, where 

 the means of estimating distance is reduced to ocular convergence 

 alone, the estimate is very imperfect and uncertain. Our knowledge 

 so interferes with our visual judgment that we are apt to over-esti- 

 mate the distance. In fact, many persons even find a difficulty in 

 seeing the combined binocular image any nearer than the two mo- 

 nocular images. As long as attention is fixed on the combined cir- 

 cle, the homogeneous image of the needle will seem beyond, as it 

 ought. This will be much more distinct if we range the point of 

 sight back and forth, combining successively the needle-points and 

 the circles. But when we transfer attention wholly to the double 

 images of the needle, these latter will sometimes appear nearer 



than the circle ; not, however, because the needle seems nearer than 

 before, but because the circle drops to the plane of the paper, where 

 it tends to go, anyhow. 



The experiment illustrated by his second figure I cannot confirm. 

 It is true that experiment with his figures as drawn in Science con- 

 firms his results, but this is only iDecause the figures are badly 

 drawn. The positions of the two small circles b and c are not 

 symmetrical. When accurately drawn, I find, on combining, that 

 the small circle and the large circle appear exactly on the same 

 plane. My son, aged eighteen, and well practised in binocular ex- 

 periments, confirms my results perfectly. Whether Mr. Hyslop's 

 original figures were imperfect, or have been only badly copied, I 

 know not ; but the wonderful distinctness with which binocular 

 combination will bring out and exaggerate the smallest differences- 

 in apparently similar figures, is well known. 



Joseph LeConte> 



Berkeley, Cal., Feb. 22. 



The Scientific Swindler Again. 

 The following from the Indianapolis fotirnal of Feb. 24 may 

 be of interest to those who have been the victims of the swindler 

 so extensively advertised by your own and other journals: "The 

 book-thief who has, under the names of W. R. Taggart, Professor 

 Cameron, Professor Douglass, and various aliases, travelled over 

 the country, representing himself as a scientific student, and borrow- 

 ing valuable books, has been arrested in Cincinnati, where he gave 

 the name of Otto Syrski. He was recognized yesterday by Profes- 

 sor Collett of this city, who was one of his victims. Professor Col- 

 let learned where his books had been sold, and will probably recover 

 them." It is to be hoped that this will stop his operations, at least 

 for a time. A. W. Butler. 



Brookville, Ind., March i. 



A Critique of Psycho-Physic Methods. 



Dr. Joseph J astro w, in the second number of Xhe Jom-nal of 

 Psychology, discusses the principal psycho-physic methods now in 

 use, and advocates a thorough reform of the science of psycho- 

 physics. One of the principal conclusions at which he arrives is 

 that no such thing as a differential threshold exists ; that is to say, 

 that there is no definite point at which the difference of two sensa- 

 tions ceases to be perceptible. Dr. Jastrow's arguments fail to con- 

 vince us. He says, " The threshold is described as a point not ex- 

 actly constant, but nearly so : above it all differences can be felt, 

 below it all differences vanish into unconsciousness. No matter 

 whether little or much below this point, they are utterly lost. It is 

 idle to say, as Fechner at times does, that they differ in the amount 

 of additional stimulation necessary to bring them up into conscious- 

 ness, unless you mean that the series below the so-called threshold 

 is an exact continuation of the series above it ; and, if you do mean 

 this, then the threshold loses all its distinguishing peculiarities, and 

 ceases to exist." Further on, in discussing the theory of the right and 

 wrong cases, he says, " It has been proved that the ratio of wrong- 

 answers increases as the difference between the stimuli decreases ; 

 but the ' threshold theory ' claims that this last fails to hold after 

 this difference has been diminished below a certain ratio." 



In considering these objections, I may be allowed to treat two 

 classes of sensations separately : first, the judgment that a difference 

 exists is based on a sudden change in the character of the sensation 

 either in space or time ; second, the judgment refers to sensations 

 separate in space or time or in both. As an example of the former, 

 we may assume two adjoining fields of various colors or various in- 

 tensities of light, or a sound suddenly increasing in intensity or 

 height. The threshold theory says there is a certain difference be- 

 tween these adjoining sensations below which no difference will be 

 perceived. Practically this is admitted by Jastrow. In trying ta 

 meet such an argument, he first says that there exists only an aver- 

 age threshold ; i.e., the average smallest perceptible proportion of 

 intensity or wave-length of the two sensations on which the ob- 

 server is able to form a judgment. He continues, "Here j-ou either 

 (i) tacitly assume that not many observations are to be taken, or 

 that (2) no matter how many observations were made, no mistake 

 would ever occur." 



The arguments of the advocates of the threshold heory are 



