March 2, 1893J 



NA TURE 



421 



compressed air gives rise to an image on the plate, in 

 which there is a dark hne and a light line within it. 

 Similarly a wave of rarefaction must produce a light 

 line with a dark one within it.^ An examination of the 

 photograph F'ig. 7 will make it evident that not only is the 

 head wave a wave of compression, but the wave, which 

 starts from the end of a kind of venacontracta behind the 

 bullet, is also a wave of compression. It is a curious fact 

 which requires explanation that the head and tail waves 

 are not parallel to one another, and they do not show any 

 sign that they would become parallel if they were continued 

 indefinitely. This can only be due to either the tail of 

 the bullet travelling considerably faster than the head, or 

 to the actual velocity of propagation of the tail wave being 

 less than that of the head wave. The eftect observed is 

 true and is not optical, being neither due to the refractive 

 effect of the outer shell disturbing rays which are 

 tangential to the inner shell, nor to an effect of perspective, 

 for though the projection of a cone from a point upon a 

 plane is only seen of the proper angle, when the per- 

 pendicular, dropped from the point upon the plane, passes 

 through the vertex of the cone, yet when, as in the case 

 of Fig. II, where it passes within both cones, and more 

 within the outer one than the inner one, the effect is to 

 make the projections of both of a greater obtuseness, and 

 of the outer one to a greater extent than the inner one ; 

 nevertheless an examination of the amount of this effect 

 of perspective made by Mr. Barton showed that the 

 distortion was not sufficient to be noticeable, as the 

 difference in the acuteness of the cones certainly is. 



{To be continued.) 



NOTES. 

 Admission to the Croonian Lecture, which Prof. Virchow, 

 as we have already announced, is to deliver before the Royal 

 Society at 4.30 p.m. on the i6th inst., will be by ticket, which 

 may be obtained from the assistant secretary by introduction of 

 a Fellow of the Society. 



There will be widespread regret at the announcement which 

 we now make that the distinguished geologist, Prof. K. A. 

 Lossen, of Berlin, died there on the 24th ult. He had been 

 ailing for some time, and suffered severely before he entered 

 into his rest. In spite of the deafness which necessarily re- 

 stricted his intercourse with men of science, he had formed a 

 wide circle of friends who learned to appreciate the simplicity, 

 candour, and geniality of his character, while at the same time 

 they came to respect and admire more and more his wide range 

 of knowledge, and that marvellous aod apparently intuitive per- 

 ception of the true characters of rocks which made him probably 

 the best field-petrographer in Germany. 



We have received news of the death of Cav. Giuseppe 

 Antonio Pasquale, for many years professor of botany in the 

 University of Naples, and director of the botanic garden. Prof. 

 Pasquale was the author of numerous articles on botany and 

 cognate subjects. His earliest works of which we have 

 cognisance were on the flora of Capri (1840), and the flora of 

 Vesuvius (1842). In 1869 he published a more complete 

 " Flora Vesuviana, confronte con quella dell' isola di Capri." 

 He appears to have been appointed to the post of director of 

 the Naples Botanic Garden in 1866, and the following year he 



■ It may be worth while to point out that the dark and light lines are, and 

 ought to be, parallel to one another as soon as they are so far away from the 

 shadow of the bullet as to be practically straight lines. For if the thickness 

 of the shell is divided up into a series of elements the ray passing through 

 any one of these will meet with a refractive medium, which is less effective 

 as the diameter of the part of the shell considered is greater, while the 

 refractive angles of the elemenury prisms become inclined more so as to 

 compensate for the diminished density. 



NO. 12 18, VOL. 47! 



published a catalogue of the plants cultivated there, together 

 with a brief history of the garden. 



The German Government has established a biological 

 Institute on the island of Heligoland, and has appointed 

 Dr. Kuckuck its botanical director. 



Prof. Schweinfurth landed at Port Said on January 7, 

 for an expedition into Upper Egypt which is intended to extend 

 over several months. Dr. D. Riva, who accompanied Schwein- 

 furth on his last journey, has undertaken an expedition to 

 Eastern Africa in the vicinity of the river Giuba. 



The moss-herbarium of Dr. Rehmann and the Hepaticae- 

 herbarium of Dr. Gottsche have passed into the possession of 

 the Botanical Museum of Berlin ; the Botanical Museum of the 

 University of Vienna has acquired the moss -herbarium of 

 Hoppe ; and the Botanical Institute of the German University 

 at Prague the greater part of the valuable library of Prof. 

 Willkomm. 



The Reale Instituto Veneto di Scienze, lettere ed arti proposes 

 the following prize subjects :—(i) A lithological, mineralo- 

 logical, and chemical investigation of the rocky, sandy, earthy 

 and saline materials brought down under various conditions by 

 one of the chief rivers of Venetia from the Alpine valleys, and 

 deposited at various distances from the base of the Alps to the 

 sea (prize, 3000 lire, date December 31, 1893). (2) A com- 

 pendium of the history of mathematics, with a mathematical 

 chrestomathy containing extracts from mathematical works of 

 antiquity, the middle ages, the renaissance, and recent times 

 down to Gauss (indicating in each case the reason for introduc- 

 ing the extracts), prize and date the same. Papers may be 

 written in Italian, Latin, French, German, or English, and are 

 to be sent in to the secretary with motto and sealed packet. 



Sir Andrew Barclay Walker, who died on Monday, did 

 much to promote intellectual life in Liverpool. The University 

 College of that city has good reason to remember him a^ one of 

 its most generous benefactors. He assumed the entire pecuniary 

 responsibility for the erection of the Walker engineering labora- 

 tories, which cost about ;^20,ooo. 



Mr. O. M. Edwards, who was appointed to investigate the 

 various conditions which have to be taken into account in con- 

 nection with the proposal for the establishment of a Welsh 

 University, has completed his inquiries and forwarded his re- 

 port to the Vice-President of the Committee of Council on 

 Education. A writer in the University Correspondent says the 

 report is practically a pamphlet of about eighteen octavo pages, 

 containing a short account of the origin and progress of the 

 educational movement in Wales, and intended to supplement 

 the information already possessed by the Department of Educa- 

 tion on this head. It contains a succinct epitome of the various 

 schemes proposed — the Shrewsbury Charter, the proposals of 

 Dr. Roberts And Prof. Evans ; gives the state of efficiency of 

 Lampeter and the three Welsh colleges ; contrasts them with 

 those at Leeds and Manchester ; and points out how far, more 

 or less, the Welsh institutions are prepared and adapted, in 

 point of staff", students, accommodation, and appliances, to 

 receive similar powers. 



The Municipal Council of Paris has been giving names to 

 some new streets, and changing those by which various old streets 

 have hitherto been known. The names selected for use are for 

 the most part those of illustrious Frenchmen, and it is significant 

 that among them are some well-known men of science. The 

 Rue du Battoir, for instance, is henceforth to be called the Rue 

 Quatrefagcs, in memory of the famous anthropologist ; and the 

 Rue Claude- Vellefaux becomes the Rue Charles-Robin, in 

 memory of the great physician. A new street is called after 



