136 



SCIENTIFIC NEWS. 



[Feb. 10, 18 



cialists. The Riigosa, otherwise known as Tetracoralla, 

 form an important group among the corals. They are 

 described as appearing lilce a series of cups, one within 

 another, generally increasing in diameter as they ascend, 

 and surrounded by a wall enclosing the septa. These 

 septa, in some of the genera, present peculiar out- 

 growths known as carinae, and these Miss Holmes has 

 made the object of especial study. She shows that they 

 are not inorganic structures, casually attached to the 

 septa, but are normal out-growths, though not homolo- 

 gous with any of the structures usually recognised in 

 these beings. She considers that their full functional 

 value has not yet been determined. We next find a de- 

 scription of their structure in upwards of forty species 

 of corals. The treatise is illustrated with thirty-four 

 figures, mostly drawn from nature. 



Expansion of Structures by Heat. By John Keilly, late 

 of Indian Public Works and Victorian Railway De- 

 partments. (London : Crosby Lockwood and Co.) 

 This is a useful book for the civil engineer. It com- 

 mences with simple formulae and tables of coefficients ot 

 expansion, and fully worked-out examples of the expan- 

 sion of a steel tape, a wrought-iron girder, a wire 

 pendulum, and a lead pipe are given. The effects of the 

 force of expansion are dealt with in a very clear style, 

 and a table is given showing the force exerted in expand- 

 ing or contracting by a bar one square inch in sectional 

 area for a variation of temperature of one degree, and 

 the variation of temperature required to produce a force 

 of one ton in a bar of this size. It is shown that, when 

 the barrel of a gun becomes heated, the bore does not 

 contract, as stated in some works on musketry, but it 

 expands. " During the late campaign in the Soudan it 

 was found that, after firing, the charge would not enter 

 the barrel of the breech-loader in many instances. This 

 was attributed to the presence of grit from the sand, but 

 it appears probable that another solution can be found 

 for the difficulty. Soldiers' pouches are covered with 

 black glazed leather, and, when exposed to the sun of 

 the Soudan, some of the ammunition in them would be 

 raised to almost as high a temperature as the barrel of 

 the rifle. But the ratio of 



the expansion of lead _o'ooooi62 _^. , 

 the expansion of iron o"ooooo686 

 — that is to say, for the same variation of temperature 

 the leaden bullet would expand two and a-third times as 

 much as the iron barrel of the rifle ; whence, if it be as- 

 sumed that the machine-made bullets were just a fair fit 

 for the rifles at the temperatures common in England, 

 they would possibly not fit when under different circum- 

 stances in the Soudan or in India." 



A considerable number of examples throughout the 

 book are worked out in full, figure by figure, but the 

 author deals only with purely civil engineering, where 

 the greatest range of temperature is from 215 degrees in 

 the sun to a few degrees below zero in a hard frost. The 

 mechanical engineer will not find any examples of the 

 effects of expansion in steam boilers, etc., though the 

 tables given will, of course, be equally useful to him. In 

 iron structures — such, for example, as the Crystal Palace 

 — it is only in exceptional cases that special calculations 

 need be made for the strains caused by an unequal dis- 

 tribution of temperature. A short chapter is devoted to 

 a modification of the construction of suspension bridges, 

 which does not appear very feasible even on a 

 moderately large scale. It is proposed that the piers 



should be attached to the member forming the road, and 

 that the whole bridge, road, piers, chains and all, should 

 be free to expand and contract, presumably on rollers. 



Playground of Science : A Series of Novel and Interesting 

 Scientific Experiments. By Johnston Stephen. Lon- 

 don : Truslove and Shirley. 

 The author of this little book evidently aims chiefly at 

 the young, into whom he seeks to instil a taste for 

 experimental science under the guise of amusement. It 

 is his evident hope, and our belief, that he will be not 

 unsuccessful. The experiments which he describes can 

 be performed easily and cheaply, and some of them are 

 of a very novel character. Under the head " Chemical 

 Vegetation," he (the author) gives a process which we 

 saw performed by its discoverer, M. Georges Fournier. 

 The forms produced are certainly much closer imitations 

 of living things than the lead or silver trees, with which 

 young experimentalists are often amused. We find in 

 them, as in plants and animals, vessels or cells whose 

 contents differ in nature from the walls in which they 

 are enclosed. They display, in short, a certain beginning 

 of differentiation. But in what it may end we cannot 

 say. The book will, we think, form a very appropriate 

 present for boys of an inquiring turn of mind, who will 

 draw conclusions from what they see. 



*-?»^^5*f-» ■ 



THE RATE OF ANIMAL DEVELOP- 

 MENT.— I. 



ONE of the attempts made to prove the existence of 

 a "great gulf" severing man from the rest of 

 creation is exceptionally curious as an instance alike of 

 bad observation and of hasty reasoning from defective 

 premisses. That by such arguments men of eminence 

 could mislead themselves and succeed for a long time 

 in misleading the public is at once suggestive and 

 humiliating. Professor St. George Mivart suggests 

 (" Lessons from Nature ") that a book ought to be 

 written on the " Stupidity of Animals." Should the 

 needful companion volume on the '' Stupidity of Man- 

 kind " follow in due course, it might verj' suitably open 

 with the reasoning we are about to quote. 



To begin then : The slow bodily development of the 

 human infant, and its prolonged helplessness, are mat- 

 ters far too familiar to require description. No less 

 familiar and generally admitted is the rapidity with 

 which foals, calves, lambs, kids, chickens, and ducklings 

 acquire the use of their limbs and other organs. Such 

 facts could not fail to come under the notice even of 

 very careless observers. But who would have supposed 

 that such characteristics would be, without further 

 scrutiny, at once seized hold of as a fit theme for stilted 

 declamation, and be elevated to the rank of a funda- 

 mental distinction between man and beast ? Yet this 

 gross error was actually committed, not merely by men 

 of words, " talkers of talk " — which was bad enough — 

 but even by a man of things, like Sir Humphrey Davy ! 

 The great chemist, in his " Salmonia," attempts to show 

 that man does not use his limbs instinctively, like other 

 animals. Quoth he, " Man is so constituted that his 

 muscles acquire their power by habit,* but in the colt 

 and the chicken the limbs are formed with the power 



* Every one knows that a muscle is strengthened by habit ; but if 

 it were originally without power " habit" would be impossible. 



