HARDWICKE'S SCIENCE-GOSSIP. 



79 



approaches within one short step to cellulose, the 

 material of the cell-walls, or the general basis of the 

 organised structure of plants. 



" The Gift of the Nile." — Sound geological 

 philosophy is profoundly indebted to Sir Charles 

 Lyell, who not only hammered at rocks, but, 

 hammered, hammered, ami hammered, most perti- 

 naciously at the heads of his contemporaries to insert 

 therein the fundamental geological principle, that 

 " causes similar in kind and energy to those now 

 acting, have produced the former changes of the 

 earth's surface." " The Principles of Geology " — his 

 main hammer — still remains, in my estimation, the 

 most fascinating scientific treatise that has ever been 

 ■written. The multitude of facts, all intensely in- 

 teresting, and admirably arranged, is astonishingly 

 great ; the book is a monument of industry in their 

 collection. It is written with such simplicity and 

 clearness throughout that anybody may read and 

 understand every paragraph without any previous 

 technical training. If any of my readers have not 

 yet read it, I exhort them to commence at once at 

 Chapter I., and go steadily through to the end. 

 Whether they have read all the newer geological 

 treatises, or no geological treatise whatever, they will 

 be far wiser after reading Lyell's book than they were 

 before. 



These remarks are suggested by a work which is 

 now in hand, viz. the Royal Society's borings in the 

 delta of the Nile, which have gone considerably 

 beyond 300 feet in depth without reaching the rock 

 which forms the bed of the marine valley which this 

 river has filled up with a deposit of almost continen- 

 tal magnitude, and has done it all during the present 

 geological epoch. Egypt is " the gift of the Nile," 

 and in spite of its great magnitude all this deposit is, 

 geologically speaking, but the work of to-day. It is 

 demonstrable that the great river has flowed in its 

 present course with similar geological results, un- 

 disturbed by any great upheavals or other cata- 

 strophes, ever since it fell Niagara-like over the 

 rocks of a sea coast which are now more than one 

 hundred miles inland. 



Snow Clothing.— Seventy to eighty degrees 

 below zero, i.e. thirty to forty degrees below the 

 freezing-point of mercury, is a temperature we can 

 scarcely contemplate without a shudder, yet such 

 was endured in Siberia by Captain Wiggins and his 

 crew last October. 



It is in such a climate as this that the beneficence 

 of snow is fully manifested. The snow falls heavily 

 at the beginning of winter, while the surface of the 

 ground has not yet fallen below thirty-two degrees, 

 the snow itself being at about that temperature, 

 or say thirty degrees. The feathery crystals and the 

 air they entangle are nearly absolute non-conductors 

 of heat, and constitute the most effective of all 

 possible clothing. Thus the soil in such countries 



never falls to so low a minimum temperature as it 

 occasionally reaches in England when we have a 

 temperature of fifteen to twenty degrees over naked 

 ground. Hence the paradox of Siberian vegetation, 

 which is so luxuriant in the summer, when the heat 

 of the long days is very intense. 



Do Birds Sleep on the Wing?— This question 

 has been seriously propounded in the New York 

 National Academy of Sciences, where Professor 

 W. P. Trowbridge read a paper describing his son's 

 discovery, that birds of prey and some others have 

 the power of locking securely together those parts 

 of the wing which affect the extension of the 

 feathers, and correspond to the fingers of the human 

 hand. The wings are thus kept in the soaring 

 extension and position without any muscular effort. 

 At first thought, the idea that a bird should maintain 

 its delicate balance even during a few minutes' doze 

 appears extravagant, but the idea assumes a different 

 aspect after a little reflection. It is well known that 

 men have fallen asleep while walking, and have thus 

 walked some distance. I know a case of a farmer 

 who has fallen asleep on horseback without falling 

 off when returning home after market dinner. We 

 can all understand the possibility of sleeping while 

 standing upright or even walking, and those who 

 are accustomed to the saddle can understand the 

 farmer's exploit, but, on the other hand, there are 

 some among us who cannot keep the saddle even 

 when very wide awake. A dog that has just learned 

 to sit on its haunches and beg, would not be able to 

 sleep in that position. 



These possibilities simply depend upon whether 

 the action in question, flying, walking, standing, or 

 riding, has become automatic. Regarded theoretically 

 the art of balancing the human body on so small a 

 base as the human feet is one of marvellous muscular 

 complexity, but practically it is so easy as to be per- 

 formed without any conscious effort. Theoretically 

 regarded by us the art of flying and soaring are 

 extremely difficult, but practically they are doubt- 

 less as easy to the bird as walking and standing are 

 to us, and therefore may be performed as automatically. 

 Admitting this, it is still very improbable that the 

 bird can do any more than " forty winks," a semi- 

 conscious after-dinner snooze while in mid-air. 

 Taking a night's rest, or even a fraction thereof, is 

 very different. 



Energetic Ballast. — Electric accumulators are 

 subject to a serious objection. The plates in which 

 the latent energy is stored are of lead, and a great 

 surface of this being demanded they are very heavy : 

 their use is restricted accordingly. But there is one 

 case where a heavy weight is desirable, in fact 

 necessary; this is in the ballasting of ships. With 

 accumulator ballast and a little dynamo to charge if, 

 a yacht or other vessel may be supplied with a reserve 

 of energy available for lighting. It might even supply 



