POPULAR MISCELLANY. 



571 



introduced into the dado space at a low level 

 and in a lateral direction to promote dif- 

 fusion, through a number of inlets from the 

 outer atmosphere along the whole line. The 

 total area of these inlets is proportioned to 

 the area of the hot-air shaft provided for 

 carrying off the impure air. The total 

 space inclosed by the dados is much greater 

 than the total area of the inlets from the 

 outer atmosphere ; and by this means the 

 entering air is made to spread itself slowly 

 through the interior of the reservoir, and to 

 percolate gently through the gauzes so as 

 to permeate the atmosphere of the room by 

 gentle diffusion, instead of entering in a 

 stream. In winter the air admitted may be 

 warmed by a heating surface of pipes fitted 

 along the length of the dado. For carrying 

 off the impure air, a chimney of suitable ca- 

 pacity is provided, with a close-throated fire 

 grate ; or a connection is formed with any 

 existing perpendicular flue. There should 

 be an opening in the room, at a high level, 

 into an outlet tube communicating with the 

 perpendicular column of rarefied air in the 

 chimney or flue. When a suitable chimney 

 or upright flue is not available, the same 

 results are produced by a suitable tube 

 erected above a skylight in the roof of the 

 hall, in which a current may also be pro- 

 moted by means of a Bunsen burner. 



Labor as a Means of Human Improve- 

 ment. The remark which has been a long 

 time current is re-enforced by the latest stud- 

 ies, that the prevailing and dominant people, 

 races, or nations, and the flow of superior 

 human energy have always come from the 

 cold, bleak, inhospitable regions of the north. 

 Notwithstanding physiology indicates a tropi- 

 cal or subtropical origin for mankind, man in 

 the tropical regions makes no advance, but 

 tends, on the whole, to decline ; and when 

 men from the temperate zone settle in tropi- 

 cal regions, they are very liable to become 

 enervated. The probable reason for this 

 tendency is that living in such regions is too 

 easy, and that the conditions prevailing there 

 do not afford the stimulus to the exertion 

 without which it is impossible to keep up 

 vigor. So, when, anywhere, a hard-working, 

 active people meet with fortune and settle 

 into a life of ease, they begin at once to 

 weaken. In England, it is the common 



people who are multiplying rapidly and 

 swarming all over the earth ; while the aris- 

 tocracy can not even keep up its stock, but 

 has to be refreshed from time to time by the 

 interpolation of fresh blood. These facts 

 are used by Prof. Williams to enforce the 

 maxim that every human being should earn 

 his daily bread by daily work, and that the 

 inheritance of such an amount of wealth as 

 shall render a man or a woman a mere pur- 

 poseless pleasure-seeker is a most degrading 

 curse. 



Aniline Photographs. Analogous to the 

 photographic process with the salts of silver 

 is the production of pictures by a similar 

 process with the aniline colors. As described 

 by Messrs. Green, Cross, and Bevan, in the 

 Society of Arts, the simplest method of pro- 

 ducing a picture in any of these colors is 

 based upon the fact that they all fade more 

 or less on exposure to sunlight. Prints ob- 

 tained by exposure to sunlight of paper 

 coated with eosine and methylene blue were 

 exhibited by the authors, in which the gra- 

 dations of shade were exactly reproduced; 

 those parts which received the most light 

 were the most bleached, whereas the shadows 

 of the object had protected the parts of the 

 paper beneath them, and the depth of the 

 shadow of the original was thereby repro- 

 duced. These pictures have no practical 

 value, because they are destined to be ob- 

 literated by the gradual fading out of the 

 whole surface. In the diazotype process, 

 the picture is fixed by causing a compound 

 to be formed which will resist the further 

 action of the light. The process starts with 

 the yellow body called primuline a sub- 

 stance constituted with ammonia, having one 

 of the hydrogen atoms replaced by a com- 

 plex group. It combines with nitrous acid 

 to form a diazo compound, and this, like the 

 other diazo derivatives, exercises a construct- 

 ive or synthetic reaction with the amines and 

 phenols, with which azo-coloring matters are 

 formed. The essential conditions of pri- 

 muline photography are that the reactions 

 take place with primuline after its applica- 

 tion to any surface or material as a dye, 

 without affecting its union with the material ; 

 and that the diazo derivative produces the 

 photo-sensitive in the highest degree. The 

 prints obtained are positive, the light and 



