MISCELLANY. 



251 



of hyposulphite of soda and a mercurial 

 compound in such proportions that the bi- 

 sulphide of mercury is slowly deposited, the 

 deposition being almost entirely suspended 

 until the print containing the unreduced 

 chloride of silver is added to the solution. 

 The withdrawal of hyposulphite to dissolve 

 the chloride causes the deposition of the 

 bisulphide to take place in the print." Pict- 

 ures obtained in this manner resist strong 

 reagents in a way that gives promise of 

 great permanence, while they have a rich 

 tone, and a novel and fine effect. Mr. 

 Sherman has been experimenting a good 

 deal on the precipitation of vermilion, and 

 finds the color of the product powerfully 

 affected by light. 



THE SUN'S ATMOSPHERE. 



Dr. Janssen, the French astronomer, in 

 a letter to Prof. Newton, of Yale College, 

 an extract from which is published in the 

 American Journal of Science and Arts, says 

 of the sun's atmosphere : " My observations 

 prove that, independently of the cosmical 

 matter which should be found near the sun, 

 there exists about the body an atmosphere 

 of great extent, exceedingly rare, and with 

 a hydrogen base. This atmosphere, which 

 doubtless forms the last gaseous envelope 

 of the sun, is fed from the matter of the 

 protuberances which is shot up with great 

 violence from the interior of the photo- 

 sphere. But it is distinguished from the 

 chromosphere and the protuberances by a 

 much smaller density, a lower temperature, 

 and perhaps by the presence of certain dif- 

 ferent gases." Janssen proposes to call 

 this the "coronal atmosphere," as he con- 

 siders it to produce a large portion of the 

 phenomena of the solar corona. 



SCIENTIFIC! ADVANCE IN GERMANY. 

 Prof. Virchow, in his address before 

 the Congress of German Naturalists, states 

 some facts which show what progress free- 

 dom of discussion has made in Germany 

 since the beginning of the present century. 

 " Not perhaps at the dead of night, but still 

 beneath the veil of secrecy, a kandful of 

 savants assembled for the first time at Leip- 

 Bic, at the invitation of Oken. In fact, in 

 1822, no considerable body of men could 

 come together in Germany, in answer to a 



public invitation, with the permission of the 

 civil authority. They could not discuss 

 among themselves scientific questions, no 

 matter how unconnected with the political 

 and national questions of the day. Add to 

 this that other fact, that, if I am not mis- 

 taken, it was only in 1861, at the Congress 

 of Naturalists at Spires, that the names of 

 the Austrian members could be made pub- 

 lic, and then we can appreciate the tremen- 

 dous change that has been brought about in 

 Vaterland." In the same address Dr. Vir- 

 chow pays a well-earned tribute of honor to 

 French savants. He opposes also the sug- 

 gestion that has been made by certain Ger- 

 man professors, that brevets, or honorary 

 memberships of French Academies, etc., 

 held by German scientific men, should be 

 sent back, for the reason that a distin- 

 guished French botanist had recently de- 

 clined the honor of being made an asso- 

 ciate of the Natural Science Academy of 

 Leipsic. 



ACTION OF SEWAGE- GAS ON LEAD 

 PIPES. 



Dr. Andrew Fergus states that lead soil- 

 pipes are often found corroded and even 

 perforated in positions which justify the be- 

 lief that the destructive agent is sewer-gas. 

 The corroding action always takes place 

 from within, and is generally confined to 

 the upper surface of the pipe most frequent- 

 ly in those situations where it lies in an hori- 

 zontal position, though vertical pipes and 

 the upper surfaces of bends are sometimes 

 affected. Among the diseases he has ob- 

 served as resulting from this state of things, 

 typhoid fever, diphtheria, scarlet fever, and 

 diarrhoea, are mentioned. 



COOLING AND VENTILATION OF RAIL- 

 WAY-CARRIAGES. 



An ingenious contrivance for excluding 

 dust and cooling the air of railway-carriages 

 in hot countries is described in a late num- 

 ber of Engineering. It consists of an ar. 

 rangement attached to the under side of 

 the carriage, into which air is admitted and 

 made to pass between layers of material 

 that are kept constantly wet by a supply 

 of water from above, and that present a 

 large evaporating surface. By this means all 

 dust is arrested in the chamber, and the ail 



