28 



SCIENTIFIC NEWS. 



[July 13, i? 



When driven within the limits of" speed best suited for 

 ventilating buildings, the air is moved at the rate of about 

 15,000 cubic feet per minute per horse power, and this 

 is certainly an excellent performance. The higher the 

 speed the greater is the power required for a given 

 volume, and a large size run slowly is better than a 

 smaller size driven quickly, unless considerable resist- 

 ance has to be overcome. 



Besides ventilation, the Blackman propeller is largely 

 used in many industries for drying purposes, such, for 

 instance, as the drying of cloth, timber, paper, wool, glue, 

 etc. In many cases the heated air drawn from one part 

 of a building may be used for drying or warming in 

 another, or the air to be used for drying may be made to 

 pass over heated pipes. One firm of furniture makers 

 have four drying chambers, in which about twenty tons 

 of timber are dried weekly by means of heated air 

 drawn through them by two Blackman propellers. The 

 temperature of the chambers is maintained at about 

 8o° Fahr., and the timber is said to be in good condition 

 for working when taken out, and free from cracks or 

 warps. Rooms through which heated air is drawn by 

 propellers, are also used for the drying of leather and card, 

 or mill-boards, these materials being hung as nearly 

 edgewise to the air current as is practicable. 



The dust and fumes produced in many factories are 

 highly injurious to health, and it is most important that 

 they should be removed from the workrooms. In white- 

 lead works the fumes are poisonous, and in the grinding 

 of steel and iron in the cutlery and other trades, the fine 

 metallic particles are a fruitful source of lung disease- 

 Again, the dust from wool often gives rise to the 

 dreaded wool-sorter's disease, which generally ends 

 fatally. It is caused by a minute organism called the 

 bacillus anthracis, which is conveyed by the skin or wool 

 of animals which have died of splenic fever. All these 

 dangers may be minimised by a proper system of venti- 

 lation, but, although this is well understood, it is sur- 

 prising to find it neglected, even in some of our best 

 appointed factories. 



It has been suggested that much of the fruit which is 

 lost in this country, where there is not sun enough to dry 

 it, may be preserved by air-drying. In warmer climates 

 raisins, currants, apples, plums, etc., are dried by the sun 

 after being gathered, and are then sent to England for 

 sale. In our less favoured and uncertain climate this 

 cannot be done, and fruit growers will do well to try 

 thoroughly the above suggestion of drying their fruit in 

 chambers by means of an air-propeller. 



THE AUDITORY ORGAN OF THE 

 GNAT. 



LOVERS of minute anatomy will find this a curious 

 subject for microscopic study. Capture a male 

 gnat, known by the beautiful plumose antennae, moisten 

 with alcohol, and afterwards dissect out with fine needles 

 in a drop of water. One oi the antennae is to be cut 

 off, and the large basal joint is the special subject of in- 

 vestigation. This is seen to be of almost spherical 

 shape, but flattened on its free surface, to which the 

 second joint is attached. When the second joint is 

 removed a sunk circular space is seen upon the large 

 first joint. To the bottom of this cavity the second 

 joint was attached, and the radiating muscles, by which 

 it was moved this way or that, can be made out in a j 

 successful preparation. A fortunate cut will now and | 



then reveal the true character of the basal joint, which 

 we shall describe by comparison with a more familiar 

 object, viz., a common paraffin lamp. In this the flame 

 is screened by a chimney and a globe. Suppose that 

 the upper edge of the globe is turned downwards, so as 

 to form an inner and much smaller globe, to the bottom 

 of which the chimney is fixed : the double globe thus 

 formed represents the large basal joint, while the 

 chimney corresponds to the rest of the antenna. We 

 must next suppose that the space between the inner and 

 outer globes is filled with fluid. A cylindrical wick 

 passing up the chimney would indicate the position of 

 the antennary nerve, but to complete the resemblance 

 we must further suppose that a circular fringe of fila- 

 ments, beautifully regular in disposition, passes off from 

 the outer surface of the wick, and penetrates the closed 

 fluid-containing chamber. The essentials of an auditory 

 organ have now been brought together. We have the 

 closed cavity filled with fluid, the numerous nerve-fila- 

 ments, and" the modified hairs (?) in which these end. 

 It is easy to imagine that the nerve-endings may be of 

 various lengths, each responding to a particular kind of 

 sound-wave, but we have no direct proof that this is 

 actually the case. The organ just described will furnish 

 an interesting and not too difficult subject to the micro- 

 scopist who has a little skill in manipulation. The ex- 

 ternal features of the antenna of the male gnat were 

 figured more than 200 years ago by Swammerdam in 

 his " Biblia Naturae." Its internal structure was well 

 described by Dr. Christopher Johnston, of Baltimore, in 

 vol. iii. of the " Quarterly Journal of Microscopical 

 Science" (1855). 



DYE COLOURS FROM PLANTS AND 

 SHRUBS. 



A VARIETY of very useful colours and dyes may be 

 ■^ obtained from very common plants, growing in 

 abundance almost everywhere. The well - known 

 huckleberry, or blueberry, when boiled down with an 

 addition of a little alum and a solution of copperas, will 

 develop an excellent blue colour ; treated in the same 

 manner with solution of nut galls, they produce a clear 

 dark-brown tint, while with alum, verdigris, and sal- 

 ammonic, various shades of purple and red can be 

 obtained. The fruit of the elder, so frequently used for 

 colouring spirits, will also produce a blue colour when 

 treated with alum. The privet, boiled in a solution of 

 salt, furnishes a serviceable red. The shoots of the com- 

 mon burning bush, " euonymus," when treated with sal 

 ammoniac, produce a beautiful purple red. The bark 

 of the currant bush treated with a solution of alum 

 produces a brown. Yellow is obtained from the bark of 

 the apple tree, the box, the ash, the buckthorn, poplar, 

 elm, etc., when boiled in water and treated with alum. 

 A lively green is furnished by the brown corn. — Scientific 

 American. 



The Uses of Saccharine. — According to the Medical 

 Press and Circular, the Seine Council of Hygiene has 

 received a report presented by Dr. Dujardin-Beaumetz, 

 which declares saccharine to be not an aliment but a 

 medicament. They are moreover convinced its main 

 use in industry will be in adulterating alimentary 

 products. The report was unanimously adopted by the 

 Council, and the probable result will be the prohibition 

 of saccharine in all articles of food. 



