i8o 



REVIEW OF REVIEWS. 



April 1, 1913. 



SCIENCE, MEDICINE AND MUSIC. 



WHY SAP RISES. 



The Strand contains an important 

 contribution from Mr. John J. Ward 

 and Mr. George S. Heaven on " The 

 Mystery of the Sap." The article is 

 illuminated by reproductions of micro- 

 scopic sections and photos, of experi- 

 ments which reveal some of the mysteri- 

 ous processes of nature. 



THE OLD IDEA EXPLODED. 



The writers are most painstaking in 



their explanations of the long-standing 



problem : 



How the raw sap traveLs from the absorb- 

 ing roots beneath the ground to the topmost 

 twig on an oak or elm tree, more than one 

 hundred feet above, and to nearly four or 

 five times that height in the case of some 

 of the mammoth gum trees (eucalyptus) of 

 the Tasnianian forests, and in the gigantic 

 Wellingtonia of California, has long puzzled 

 the physicist to explain. The old idea that 

 capillarity is tne factor at work, the fluid 

 being conveyed up the trunk and branches 

 after the manner of oil through the wick 

 of a lamp, becomes an altogether inadequate 

 explanation. 



THE ROOT HAIRS. 



The microscope reveals the existence 



of minute hairs on the tips of the 



roots : — 



The whole group of hairs of the root-fibre 

 may not occupy more than one-tenth of an 

 inch of its length, yet they are gathering in 

 sufficient moisture (with the mineral matters 

 of the soil dissolved therein) not only to 

 support the comparatively thick root-fibre 

 from which they spring, but also to send up 

 abundant additional supplies for the re- 

 quirements of the leaves, flowers, and fruit 

 high above ground. 



So marvellously do they absorb water that, 

 before it has penetrated many of the outer 

 layers of cells within the root-fibre, it may 

 exert a pressure there equal to three atmos- 

 pheres, or forty-five pounds to the square 

 inch. This pressure passes on the water by 

 diffusion through the successive layers of 

 ground-cells of the root until the wood-tubes 

 are reached, which during sunlight always 

 have a greater or lesser tendency to be 

 emptied of water, as it is then being con- 

 tinually I'adsed in the stem, and there con- 

 veyed to the leaves, where it is quickly 

 evaporated into the 'atmosphere. 



Tne tubes also form an almost closed 

 system, so far as the admittance of air ia 

 concerned ; in fact, if air penetrated them 

 the sap would be unable to continue its up- 

 ward course. 



THE QUALITY OF PUSHING. 



These root-hairs are by no means 



mechanical automata, but develop an 



individuality and discrimination in 



their life-work which is governed by 



the chemical requirements of their 



host : — ■ 



The root-hair, then, is a modified cell. 

 How does that cell absorb water? The 

 physicist replies, " By the process of os- 

 mosis." The protoplasm of the cell, he con- 

 tends, is a fluid of a character very differ- 

 ent from the water outside the hair, and 

 the water is consequently absorbed. 



Fortunately, man possesses in some 

 degree the same quality of pushing 

 (osmosis), although expressed in dif- 

 ferent values. 



HOW THE EGYPTIANS RAISED 

 THEIR MONUMENTS. 



How did the ancient Egyptians in- 

 stall their gigantic monuments? The 

 question has long been a puzzle to 

 modern engineers. In the Open Court 

 F. M. Barber offers a solution which 

 appears to be satisfactory. 



In the rock tomb of the surgeon 

 Psamtik at Saqqaara (about 500 B.C.) 

 was found an empty sarcophagus with 

 its 17-ton cover resting on blocking 

 sufficiently high above it to admit the 

 mummy sideways. It is an important 

 proof of how sand was actually used 

 in lowering heavy weights. The cover 

 was furnished with four projections, 

 two on each side, which fitted into 

 vertical grooves in the sides of the tomb 

 chamber. The vertical grooves con- 

 nected at the bottom with horizontal 

 grooves which in turn connected with 

 a cavity in the floor under the sarcopha- 

 gus. Immediately under the projections 

 of the cover were cylindrical wooden 

 plugs, the remainder of the grooves and 

 the connecting cavity being filled with 

 sand. After the mummy had been 

 placed in the sarcophagus the blocking 

 was removed, leaving the cover resting 

 on the wooden plugs. z\ workman then 

 went under the sarcophagus and 

 gradually removed the sand from the 

 cavity, thus permitting the sand under 

 the plugs to flow into the cavity until 

 the cover descended to its final resting 

 place on top of the sarcophagus. Occu- 

 pied tombs were afterwards found with 

 cover and plugs in place. 



