MISCELLANY. 



7 6 S 



yeast in beer ; and, if so, the seeds of the 

 fungus would be likely to develop rapidly, 

 if they came in contact with milk, or water 

 containing nitrogenous matter. * A little 

 leaven would leaven the whole lump,' and, 

 as it appears to me, in this way much dis- 

 ease may be accounted for. The micro- 

 scope, then, will enable us to make out the 

 presence or absence of this fungoid or con- 

 fervoid matter in foul water, and my own 

 observations confirm me in the view that, 

 being present, it is highly dangerous, and, 

 if its cause can be removed, and the water 

 made pure, all danger from this source at 

 once ceases, while if it cannot it should be 

 at once disused, and pure water be sought 

 for elsewhere." 



A Sun-driven Engine. — G. A. Bergh, writ- 

 ing in Poggendorff s Annale?i, on the appli- 

 cation of solar heat as a motive power, says 

 that the engine which is to serve for this 

 purpose must employ some liquid with a 

 very low boiling-point. There are several 

 such liquids — sulphurous acid, methylic 

 chloride, methylic ether, etc. Of all of these, 

 sulphurous acid best deserves attention, as 

 it has several useful properties for the end 

 in view. It is not too difficult to condense, 

 and it can be got at a moderate price. 

 Now we have got the principle on which 

 we must construct our solar engine. Con- 

 ceive a vessel, filled with sulphurous acid, 

 exposed to the sun's rays ; the tension of 

 the sulphurous-acid vapor, if the tempera- 

 ture of this vessel A exceeds that of the sur- 

 rounding air by at least 10° to 20°, must be 

 from one to three atmospheres higher than 

 that of the sulphurous-acid vapor in another 

 vessel, B, similarly filled with sulphurous 

 acid, but which has only the temperature 

 of the surrounding air. We can thus arrange 

 an engine which agrees in principle with 

 the steam-engine, with merely this differ- 

 ence, that the water is replaced by sulphur- 

 ous acid, and the fuel by the solar heat ; 

 while the vessel exposed to the sun's rays 

 represents the steam-boiler, the vessel kept 

 at ordinary temperature may represent the 

 condenser. The sulphurous acid condensed, 

 after doing work in the vessel 2?, could easily 

 be driven back, by a force-pump, into the 

 vessel A. The capability of work of such 

 a machine must naturally increase with the 



amount of heat communicated to vessel A 

 or be proportional to the surface exposed 

 to the solar rays. 



An establishment, furnished with a ma- 

 chine like this, might carry on its work 

 while there was sunshine, but, in default 

 of this, would be brought to a stand-still. 

 True, the solar heat might be replaced by 

 the heat of the air, if the temperature of 

 the air were pretty high, and one had at 

 hand a refrigerating substance like ice. 

 But, as this is not always the case, the 

 establishment should have, besides the sun- 

 machine, an apparatus which might "store 

 up " some of the work done by this. As 

 such, batterer's apparatus for condensing 

 carbonic acid might be used. If a supply 

 of carbonic acid were kept in a large gas- 

 ometer, the Natterer apparatus might be 

 fed from this. In a wrought-iron vessel, 

 thus filled with liquid carbonic acid, we 

 should thus have an enormous store of me- 

 chanical force, which might be made to re- 

 place the action of solar heat in the sun- 

 machine, partially or wholly. After work 

 done, the carbonic acid, become gaseous 

 again, might be collected in the gasometer. 

 Or, again, the sun-machine, while in action, 

 might drive an ice-machine, and might, in 

 default of sunshine, profit by the ice it had 

 produced, for maintenance of its working. 



The movements of Droscra.— Prof. Asa 

 Gray, commenting in the American Journal 

 of Science on a paper by A. W. Bennett, on 

 the movements of the glands of Droscra 

 (sundcio), remarks that the author's descrip- 

 tion of these movements does not do justice 

 to the facts, as observed by Dr. Gray him- 

 self. Mr. Bennett observed not only the 

 bending in of the glands upon the body of 

 the insect which lights on its leaf, but that 

 " the sides of the leaf had also slightly 

 curved forward, so as to render the leaf 

 more concave." With us, says Dr. Gray, 

 the leaves do much more than that. As 

 well in Droscra roiundifolia as in D. longi- 

 folia, the end of the leaf folds over upon 

 the base, or nearly like a shut hand, thus 

 fairly inclosing the captive insect. 



He adds that, when Mrs. Treat's account 

 of this infolding of the leaf was published, 

 in 1871, the discovery was thought to be 

 new. But he has since found that the in- 



