IMarch 13, 1891.] 



SCIENCE. 



145 



quired by the government by this purchase lies directly south of 

 the Capitol grounds, on the brow of the hill, and is not only valu- 

 able now, but is likely to increase rapidly, both on account of its 

 commanding position and its proximity to the Capitol. 



— If the statements in a communication to the Academic des 

 Sciences by M. Lippmann are substantiated, another step towards 

 the solution of the problem of photographing objects in their nat- 

 ural colors has been made. M. Lippmann's method is remarka- 

 bly simple, and makes use of the ordinary re-agents. The sensi- 

 tive film during exposure, as stated in Engineering of Feb. 20, 

 is floated on the surface of mercury. Suppose, now, a ray of 

 blue light, for instance, strikes the sensitive film : it will pass 

 through, and, being reflected from the surface of the mercury 

 behind, will pass out through the film again, interfering on its 

 way with the incident ray. When the two rays are in the same 

 phase, their effects will be additive, and the sensitive matter in 

 the film will be strongly acted on. At a small distance further 

 on, the two rays will neutralize each other, so that the film is 

 there totally unacted on. In this way the thickness of the 

 film is divided up into layers, on which the light has acted, half 

 a wave-length apart : and hence, when fixed and dried, it may 

 be considered as consisting of a number of thin plates, of the 

 halt the wave-length of blue light in thickness, and will there- 

 fore give rise to a blue color when seen by reflected light, just as 

 the thickness of a soap-bubble gives rise to the colors seen in it. 

 Such is a general sketch of the process as described by M. Lipp- 

 mann, who adds, however, that the sensitive silver salt, iodide, bro- 

 mide, or whatever else may be used, must be distributed through- 

 out the film in an almost infinitely divided state, and in a per- 

 fectly continuous manner. The film itself must be transparent 

 Owing to the fact that the thickness of an ordinary film is many 

 times the wave-length of a ray of light, the colors obtained are 

 said to be remarkably brilliant. They are, moreover, perfectly 

 fixed; and the prints have been exposed both to a powerful elec- 

 tric arc light and to bright daylight without any signs of fading. 

 It should be added, that, if the prints are viewed by transmittei in 

 place of by reflected light, each color is replaced by its comple- 

 mentary one. 



— The following details regarding the work reported by the 

 United States Hydrographic Office will be of interest : The dan- 

 gerous obstructions to navigation off Barnegat caused by the 

 wrecks of the Spanish steamship " Vizcaya " and the American 

 schooner "Cornelius Hargraves " were removed by the United 

 States steamship " Yantic" (Commander C. H Rockwell, U.S.N. , 

 commanding) on Jan. 29. There were thirteen fathoms of water 

 over the steamer, which lay on her beam ends. Her two iron 

 masts and one of the wooden ones were broken off close to the 

 deck ; the fourth (wooden) was afloat, with the heel about ten 

 feet above water, and head held down by the rigging. The 

 "Hargraves" was found to be nearly upright. Of her four large 

 masts, the fore was standing erect, the topmast fidded and secured 

 with massive wire rigging. The second mast was broken off 

 near the deck, and was floating with the lower part above water, 

 and surrounded by a mass of floating wreckage attached by rig- 

 ging. The third mast was also intact, like the first, and con- 

 nected with the hull by the rigging. The fourth was not visible. 

 The massive wire rigging was first cut from the mastheads and 

 towed clear of the hull, so as not to interfere with lowering the tor- 

 pedoes. This duty was performed by a party under the direction 

 of Lieut. Richman, assisted by Lieuts. Mertz and Rose, Ensign 

 Bristol, and Boatswain Sutton. The work was successfully 

 accomplished, after some delay on account of thick fog. Torpe- 

 does were carried out, attached to mast-hoops on the mast of the 

 ■"Hargraves," sunk to a depth of twelve and a half fathoms, so as 

 to rest on her deck, and exploded. The mast was broken off 

 close to the deck, and came to the surface, with a portion of the 

 deck-house or cabin. In a similar way the other masts of the 

 schooner and steamer were attacked and blown out, and on the 

 morning of the 30th the work was so far completed that careful 

 soundings taken in the vicinity showed nowhere a depth of less 

 than thirteen fathoms, with no obstruction visible. The '• Yan- 

 tic" received orders on Feb. 10 to cruise along the coast from 



Sandy Hook to Charleston, S.C, and to destroy, as far as practi- 

 cable, aU abandoned wrecks dangerous to navigation. 



— Between electricity, which turns night into day, and in other 

 ways fulfils the duty of a city full of policemen, and photography, 

 which disseminates the features of the convict far and wide, the 

 times are not so auspicious for the burglar as they used to be. A 

 citizen of Toledo, O., is accredited by the Boston Transcript with 

 an invention by which an instantaneous photograph of an incom- 

 ing burglar can be made by the flash-light camera that has been 

 previously set and focused toward the door in such a way as to 

 take in the entire figure of the intruder. The essential features of 

 the device are a camera and a flash-light arrangement, in which 

 is provided mechanism to strike a match, that ignites the flash- 

 powder. Simultaneously with the flash a pivoted spring shutter 

 is moved so as to cause instant exposure on the sensitive plate, and 

 the work is done. As the burglar opens the door and steps on a 

 prepared mat, an electrical connection is made, and a lively greet- 

 ing rings out from the alarm-bells. The burglar may retreat as 

 hastily as he pleases, but the photo flash-light has been too quick 

 for him, and his image is left behind. 



— From the official report of the Japanese census, taken on Dec. 

 1, 1889, it appears that the number of houses in the whole of Japan 

 is 7,840,873, and the total population 40,702,020. The above pop- 

 ulation divided according to classes gives the following results, as 

 we learn from Nature of B'eb. 19 : nobles and their families, 3,825; 

 old mflitary class, 1,993,637; common people, 38,074,558. These 

 figures, compared with the census taken in 1888, show an increase 

 of 38,046 houses, and of 464,786 persons. Statistics of ages are 

 also given; and from them it appears that at the close of 1889 

 there were 65 persons vvho had attained their hundredth year in 

 Japan, 45 their hundred and first year, 13 their hundred and sec- 

 ond year, 11 their hundred and third year, 1 his hundred and 

 fourth year, 9 their himdred and fifth year, 3 their hundred and 

 sixth year, 1 his hundred and seventh year, and 1 his hundred 

 and ninth year. The cities and prefectures having populations of , 

 over a million numbered 15, that of Tokio being given at 1,138,346; 

 but this includes not only the city, but also a considerable admin- 

 istrative area around. 



— D. C. Heath & Co., Boston, have just published a map of 

 Palestine, prepared in outline especially for the use of Sunday- 

 school teachers and classes. The same firm have in press for 

 eirly publication, in their Modern Language Series, an edition of 

 Eichendorff's " Taugenichts," with notes by Professor Osthaus of 

 Indiana State University; also a volume containing " LaDerniere 

 Classe," " La Siege de Berlin," and " La Mule de Pape," — three 

 ingenious stories from the pen of that clever writer, Alphonse 

 Daudet, with notes by Professor Sanderson of Harvard. 



— The Milton Bradley Company of Springfield, Mass., have 

 recently pubhshed a manual for teachers which is of more than 

 ordinary importance. It is entitled " Color in the School-Room," 

 and, besides a hundred pages devoted to the theory and practice of 

 color-teaching, it contains nearly the same number of pages of 

 colored papers prepared for primary instruction. The selection of 

 colors given includes the six spectrum standards, with intermediate 

 hues between each two standards, and a miscellaneous selection 

 of the tints and shades of the standards and various combinations of 

 them. Each tint, shade, or combination is given a name correspond- 

 ing with its color-value; as, for instance, "red tint No. 1," "red 

 shade No. 2," " yellosv-green shade," etc. This method, though it 

 will not supersede the one in common use, is doubtless the best that 

 can be devised for the purpose intended, as it gives a compact system 

 of nomenclature well adapted to the needs of both teacher and 

 pupfl, each name at once suggesting its proper place in the color 

 scheme. In the text there are chapters on the necessity of color- 

 teaching in primary schools, color definitions, color-blindness 

 (which, in some instances, is only color ignorance), the theory of 

 light and color, a standard of color, how to utilize the spectrum 

 as a standard of color, the use of rotating color-disks, the demand 

 for a definite color nomenclature, the proper combination of 

 colors, the Bradley scheme of colored papers, colored paper in the 

 school-room, and water-colors in the school-room. ■ 



