157 



EiSE OF Sap in Trees and Plants. — The nature of capillary or 

 liair-like attraction, has long been known and satisfoctorily studied. It 

 is easily illustrated by placing a lump of loaf sugar in a plate con- 

 taining a little water, when the liquid will almost instantaneously rise to 

 the sugar, even two or three inches beyond its level. On this principle 

 the rise of sap in plants and trees has been explained. The celebrated 

 philosopher, M. Berquerel, considers that electricity is an acting cause. 

 A capillary tube that will not allow water to pass through it, does so at 

 once on being electriiied, and he conceives that electro-capillarity is the 

 efiicient cause of sap traveling in vegetable life. 



Milk under the Microscope. — Apart from the adulteration milk un- 

 dergoes, there are several changes that unlit it for food. If the surface 

 of fresh cream be examined under the microscope, M. Essling finds that 

 just such appearances are presented as are seen in most substances un- 

 dergoing putrefaction. In summer such a change takes place in from 

 fifteen to twenty-four hours after milking, and in winter it will be per- 

 ceptible after the lapse of two or three days. If the observation be 

 continued until the moment of coagulation, the corpuscles increase in 

 number, from ramified chains, and at length are transformed into regu- 

 lar mushrooms or filaments composed of cells placed end to end in sim- 

 ple series, and supporting at their extremities a spherical knob filled 

 with grain-like matter. M. Essling thinks that such may be classed 

 among the Ascophora. The first appearance of these spores occurs be- 

 fore the milk gets sour, and as children largely feed on milk it is possible 

 that many of their gastric affections may arise from this cause. The 

 milk of animals should therefore be drunk as soon as possible after be- 

 ing drawn, or kept in close-corked vessels until required for use, so as to 

 be entirely excluded from the external air. 



Velocity of Insects' Wings during Flight. — M. E. Marey has 

 made some curious inve'stigktions on this subject. Much doubt has 

 arisen as to the cause of the humming sound produced by insects, but 

 which is generally supposed to be caused by the vibrations of the wings 

 during flight. To ascertain their velocity, M. E. Marey adopted the fol- 

 lowing plan : The insect was grasped at the back by a pair of fine nip- 

 pers, and when it sought to fly one of its wings was directed in such a 

 way that it rubbed its point against the surface of a smoked cylinder 

 which revolved with a known velocity. The wing at each of these revo- 

 lutions carried away a little of the black smoke which covered the 

 cylinder, and left a trace of its passage. The result of the experiments, 

 allowing in regard to their accuracy for a variety of distracting causes, 

 was to show the following number of beats per second for the wings of 

 each insect : The common fly 330, the drone 240, the bee 190, the wasp 

 110, the hawk-moth 72, the dragon fly 28, and the cabbage-butterfly, 

 which is inaudible, 9 beats per second. By other variations of the ex- 

 Ijeriments he arrived at similar results. 



Oyster culture. — The enormous j)rice of oysters during the past 

 few years has greatly stimulated their artificial culture. Very recently 

 some interesting experiments have been conducted by Captain Ross, chair- 

 man of the Brading Harbor Oyster Fishery Company, at the Isle of 

 Wight. The first attempt was directed to discover the nature of the 

 favorite food of the oyster, and for this jiurpose two cisterns were fitted 

 up to contain the animal. One of these cisterns was supplied with fil- 

 tered sea- water, the only vegetable matter present being a few pieces of 

 sea-weed. The other tank was supplied with water direct from the 

 harbor. Another tank was fitted up as a kind of infirmary, to which 

 the parent oyster was committed during the process of its emitting 



