May 2, 1890.] 



SCIENCE. 



277 



try is more densely settled than it was one or two decades ago, 

 and many local storms would now be observed where they could 

 not have been seen and reported some years ago. Thus, the 

 average number of tornadoes reported annually for the last ten 

 years is 159, while for the previous ten years it was only 45. 

 For this reason, it would not be safe to compare the spots with 

 any former cycle. In order to make the figures for 1878-89 fairly 

 comparable, those for the first three or four years may be raised 

 slightly, perhaps; and those for the last two may be increased 3 

 or 3 per cent by belated returns. The annual average, then, would 

 be more than 160 (say 170), with minima at the ends of the series, 

 and a maximum near the centre: — 



Another curious fact is that the greatest number of tornadoes 

 reported upon one day, according to Finley, was 60, on Feb. 19, 

 1884. Wolf's relative number for January, 1S84 (9i.l), is the 

 largest for any month during this whole cycle, except April, 1883 

 (97.0) ; but the average for the six or seven months beginning 

 with October, 1883, is much greater than for any similar period 

 in 1883. Tacchini (says Nature, July 1, 1886, p. 194) fixes the 

 height of solar excitement in February, 1884; but Professor P. M. 

 Garibaldi of Genoa quotes Tacchini as placing the maximum in 

 May, 1884. The maximum of protuberances found by Tacchini 

 (Nature) was in March, 1884, though Garibaldi says June-August, 

 1884. At the Royal Observatory, Greenwich, the rotation-period 

 (37 days) containing the largest daily average spottedness in 

 twelve years, began July 4, 1883, when it was 3,037 millionths of 

 the sun's visible hemisphere; but the best two-period exhibit was 

 from Dec. 14, 1883, to Feb. 7, 1884, when the daily mean was 

 1,817 millionths. The greatest facular displays recorded in the 

 Greenwich " Results " were in the rotation-periods beginning 

 Dec. 14, 1883 (3,151 millionths) and Feb. 7, 1884 (3,467 mil- 

 Uonths). Garibaldi, at the Royal University, Genoa, recorded 

 the greatest magnetic variation (in the needle's daily swing) in 

 April-July, 1884, and from August, 1885, to April, 1886. At To- 

 ronto, the biggest magnetic storms of the maximum stage of this 

 last sunspot cycle occurred in November, 1883, September, Octo- 

 ber, November, 1884, and March, 1886. During the first seven 

 months of 1884, at Toronto, the magnetic perturbations were few 

 and slight. 



The general yearly parallel between spots and tornadoes is far 

 from proving any relation between the phenomena ; and the cor- 

 respondence between the maxima of spots, protuberances, mag- 

 netic variations, magnetic storms, and tornadoes is not very close. 

 Yet the comparison here made is not without interest. 



James P. Hall. 



Brooklyn, N.Y , May 1. 



BOOK-REVIEWS. 



Graphics, or the Art of Calculation by Drawing Lines. By Robert 

 H. Smith. Part I. London and New York, Longmans, 

 Greene, & Co. 8°. 

 This work treats of graphics as applied especially to mechanical 

 engineering. The volume before us is but the first part of the 

 complete treatise, and deals mainly with the analysis of stresses 

 in engineering structures. It is accompanied by an atlas contain- 

 ing twenty-nine plates and ninety-five diagrams, the text and the 

 diagrams being each e sential to the better interpretation and 

 ready comprehension of the other. The second part of the work, 

 which it is hoped will soon be published, will deal mainly with 

 synthetic problems, aiming more at the design than the analysis 

 of structures and machines. 



The department or branch of descriptive geometry dealt with 

 in this work, the " art of calculation by drawing lines," has assumed 

 considerable importance, so that Professor Smith's scientific 

 treatise on the subject is as timely as it is practical and compre- 

 hensive. The graphic method of computation, of course, has 

 limitations in many directions, being less useful in simple cases 

 than arithmetical and algebraic methods;, but the method once 

 thoroughly mastered, and its scope and limitations clearly under- 

 stood, it will enable those who have a knowledge of elementary 

 mechanics to utilize that knowledge to better advantage and with 

 a greater degree of thoroughness, and to apply it to many of the 

 every-day problems of engineering science without the aid of the 

 more complicated portions of algebraic and trigonometrical 

 mathematics or of the differential and integral calculus. Wher- 

 ever the method is applicable, its use will result in a saving of 

 mental fatigue, as it possesses great simplicity in many of its ap- 

 plications, leaves but little opportunity for the accumulation of 

 gross errors, and is in itself a test of its own accuracy. 



The work opens with a glossary of special terms and symbols, 

 some of which are new and possessed of advantages in the matter 

 of conciseness and precision. The introductory chapter presents 

 clearly and with evident impartiality the advantages as well as 

 the disadvantages of the method, and gives a brief sketch of the 

 theoretical development of the subject. This is followed by a 

 chapter on the instruments needed in the accurate working-out of 

 the method ; after which follow in order chapters on graph-arith- 

 metic, graph-algebra, graph-trigonometry and mensuration, com- 

 bined multiplication and summation, moments of parallel vectors, - 

 vector and rotor addition, locor addition and moments of locors 

 and of rotors, the kinematics of mechanisms, flat static structures 

 without beam links, flat static structures containing beam links, 

 and solid static structures. The diagrams in the accompanying 

 atlas are neatly engraved, and clearly printed on heavy plate 

 paper. 



AMONG THE PUBLISHERS. 

 The issue of Harper's Weekly for April 26 devotes considera- 

 ble space to the Stanley-Emin relief expedition. The article, 

 which is copiously illustrated, gives tbe whole history of the ex- 

 pedition. 



— A cheap edition, limited to a hundred thousand copies, of 

 " Tom Brown's School-Days," is annoxmced by Macmillan & Co., 

 uniform in style with their paper-covered editions of Charles 

 Kingsley's novels, of which something over a million copies have 

 been sold in the past six months. 



— One of the literary sensations of the winter in Paris was 

 Camille Flammarion's astronomical romance, " Uranie," of which 

 the Cassell Publishing Company are the American pubUshers. 

 Up to the present time, M. Flammarion has been known as an as- 

 tronomer, but now he has become a popular romancer. Mrs. Mary 

 J. Serrano, translator of " Marie Bashkirtseff : The Journal of a 

 Young Artist," has put M. Flammarion's French into English. 



— In Garden and Forest for last week, Mr. H. H. Hunnewell, 

 whose gardens at Wellesley, Mass., have been famous for a gen- 

 eration throughout the country, writes of rhododendrons and their 

 culture; Professor Greene continues his notes on the shrubs of 

 California; and the concluding portion of the review of Dr. 

 Mayr's great work on the forests of North America is given. 

 "The Woods in Spring," " WUd Plants under Cultivation," and 

 " Hardy Plants for Cut Flowers," are titles of other articles. A 

 road in Sherwood Forest is the subject of one illustration, and 

 there is also a picture of a giant Cattleya. 



— Messrs. Ginn & Co. announce as in press " Political Science 

 and Comparative Constitutional Law" (two volumes), by J. W. 

 Burgess, professor of constitutional and international law and 

 history in Columbia College. In these two volumes Professor 

 Burgess sets forth the general principles of modern political science 

 and constitutional law. The State, as sovereign organization of 

 the Nation, is sharply distinguished from the government. Gov- 

 ernment, to the author, is but one of the means through which 

 the State attains its ends. The other means is liberty. The 

 first volume treats of the Nation and the State as concepts of" 



