September 4, 1891.] 



SCIENCE. 



^ss 



LETTERS TO THE EDITOR. 



#** Correspondents are reqtiested to be as brief as possible. The vrriter's name 

 is in all cases required as proof of good faith. 



On request in advance, one hundred copies of the number containing his 

 communication will be furnished free to any correspondent. 



The editor will be glad to publish any queries consonant with the character 

 of the journal. 



A Suggestion to Rain-Makers. 



While these interesting and expensive attempts to produce rain 

 by explosions are being carried out, it should be of special interest 

 to science to ascertain what would be theii- effect when the general 

 conditions of the atmosphere are favorable for rainfall. The pro- 

 moters of these experiments show certainly great faith in their 

 theory by selecting tbe worst imaginable conditions of the arid 

 west for their playing ground ; and though faith is an excellent 

 thing, which is said to be even capable of moving mountains, and 

 though Moses, when he was brimful of faith, produced water by 

 striking a rock in the desert, still I am afraid these experiments 

 may have taxed their theory too heavily by venturing to produce 

 rain under the dry conditions generally prevailing in Texas. 



Among the absolutely necessary conditions for rainfall is this, 

 that the surface-air should not be dry; and whatever the effect of 

 explosions may be at a liigher level, the rain-drops cannot reach 

 the ground by passing through dry surface-air, and it is not con- 

 ceivable how explosions could suddenly change the dry surface-air 

 into moist or saturated air. 



But while these expensive experiments are being gone through, 

 it might be of special interest to ascertain what would be the effect 

 of explosions during a natural rain, or immediately after a natu- 

 ral rain has ceased; and I venture to predict that in the first case 

 the concussion might give a sudden impetus to the downpour, and 

 in the latter case likely produce an after-shower of short duration ; 

 and these results would be confirmatory of some experiments 

 whereby I have ascertained that condensation is procurable by 

 compression of saturated air. 



A flash of lightning has often been observed to be followed by a 

 sudden increase of downpour in its immediate neighborhood, and 

 although this is likely due to electrical rather than mechanical 

 causes, still I feel confident that a compression-wave passing 

 through saturated air would result in similar effects ; and whether 

 this is actually the fact ought therefore to be ascertained while the 

 means of doing so are at hand and while the general interest is 

 awakened on the subject, — if I may venture to make this sugges- 

 tion. Franz A. Velschow. 



Brooklyn, Aug. 31. 



BOOK-REVIEWS. 



A Treatise upon Wire, its Manufacture and Uses. By J. Buck- 

 NALL SsnTH. New York, Wiley. 4°. $3. 



So far as we know, there is no other treatise upon wire which 

 covers so much of the history and uses of the material as the one 

 before us. The manufacture of gold wire dates back at least to 

 1700 B.C. The present method of drawing wire has been practised 

 certainly in the fourteenth century in some portions of Germany. 

 From these early beginnings our author traces the history of wire 

 and its uses. It was not till 1565 that machine-drawn wire of 

 home make was available in England for the making of hair-pins 

 for Queen Elizabeth; but by 1630 the home industry had grown 

 to such importance as to lead to the total prohibition, by Charles 

 I., of the importation into England of foreign wire. 



The uses of wire are, of course, many, and to each our author 

 gives attention in turn. There are the electrical applications, 

 which call for consideration of the tensile strength of the material 

 and its conductivity; there are its uses in netting, gauze, cloth, 

 and cards; there are the pin-making industry and the manufac- 

 ture of needles; the making of umbrella and spectacle frames, of 

 springs, cycle spokes, nails, and music strings, each of which 

 makes it necessary to produce a wire having properties which 

 shall suit it to the special use. The first chapter treats of iron 

 and steel wire, the latter of which has been brought to a high 

 degree of tensile strength, with the resulting possibility of cable- 

 roads and improved means of transportation on wire-rope rail- 

 ways. 



The second chapter is devoted to copper, bronze, brass, plati- 

 num, and gold wire. This leads to the consideration of very fine- 

 wires and the question of measurement and gauging, to which- 

 last subject the third chapter is given up. The fourth chapter, on 

 electrical conductors, closes the first section of the book, which is 

 more especially on the manufacture of wire. 



The second section of the book covers the application of wire in- 

 ropes, netting, woven fabrics, fencing materials, staples, nails, etc 



The number of illustrations is large and of a character to greatly 

 increase the value of the book. 



AMONG THE PUBLISHERS. 



At the beginning of October an inci'ease of 33J per cent will 

 be made in the amount of reading-matter printed in the New 

 York Critic. 



— "An introduction to the Study of Petrology : the Igneous^ 

 Rocks," by Frederick H. Hatch, has recently been published by 

 Macmillan. This is a descriptive work of small size. The author 

 does not give any attention to the methods of examining rock 

 sections, etc., but aims to describe the mineral constituents and 

 internal structures of the igneous rocks, their mode of occurrence,, 

 and their origin. 



— John Wiley & Sons, New York, have issued a third edition, 

 of Ludlow's " Elements of Trigonometry." The author is Lieut. 

 Henry H. Ludlow, U.S.A., who had the co-operation of Edgar 

 W. Bass, professor of mathematics at West Point. The require- 

 ments of the United States Military Academy determined the ex- 

 tent and detail of treatment. The book contains both plane and 

 spherical trigonometry, and tables of logarithms of numbers and 

 the trigonometric functions. 



— Messrs. Longmans, Green. & Co. brought out not long ago a. 

 book by W. Hewitt, science demonstrator for the Liverpool school 

 board, entitled '' Elementary Science Lessons," which aims to carry 

 instruction in science into lower grades of school work than any 

 thing we remember to have seen. The first experiments are made 

 with a sheet of window-glass, a burning candle, and a glass bottle 

 or tumbler, which pieces of apparatus are made to serve many a 

 useful purpose in bringing home physical truths to the infant minds 

 during the course laid out by the author. Yet we often question 

 the wisdom of teaching'a child in the class that glass is smooth. 



— The American Academy of Political and Social Science has 

 recently published a monograph on "Recent Constitution Making 

 in the United States," by Francis Newton Thorpe, Professor of 

 Constitutional History in the University of Pennsylvania. The- 

 paper is a review of the work accomplished by the Constitutional 

 Conventions of North Dakota, South Dakota, Montana, and Wash- 

 ington. The academy has also recently published a paper on the 

 development of economic science in Italy, by Achille Loria, wha 

 is Professor of Political Economy and Statistics in the University 

 of Siena. 



— The Rural Publishing Company, New York, has recently 

 bi'ought out " The Nursery Book," which is a guide to the multi- 

 plication and pollination of plants. The author is Professor L. H, 

 Bailey of the Cornell Agricultural Experiment Station at Ithaca^ 

 N.Y. A nursery is, by Americans at any rate, understood to 

 mean a place where woody plants only are cultivated; but our 

 author designates by the word an establishment for the propaga- 

 tion of all plants. The book aims to give an account of the 

 methods commonly employed in the propagation and crossing of 

 plants; of the ultimate results and infiuences of these methods na 

 account is taken. The free use of competent criticism by experi- 

 enced propagators was resorted to by the author while writing the 

 book, and it is believed that all the methods described have met 

 with approval in this country. More than half the volume is oc- 

 cupied by a " nursery list," which is descriptive, and covers aU 

 the plants ordinarily grown by horticulturists in this country for 

 food or ornament. 



— "The Physical Diagnosis of the Diseases of the Heart and 

 Lungs, and Thoracic Aneurism," by D. M. Cammann. M.D., has 

 recently been published by G. P. Putnam's Sons, New York. 

 This book is tlie result of notes thrown together for use in teach- 



