124 



NATURE 



[November 23, 191 



dugs, and other domestic animals in various parts of the 

 world. 



For the medical or veterinary practitioner, who cannot 

 be expected to be an expert in every branch of science as 

 well as in his own art, it is of the liijjhfst imporlnncc that 

 the scientific linowledge of the ectoparasites that are likely 

 to dissfininate diseases should be brought together and 

 summarised in such a manner as to be accessible to those 

 whose vocation brings them into contact with these pests. 

 Exhaustive monographs of the various blood-sucking in- 

 vertebrates are of the greatest practical as well as scientific 

 value. The work under review is the first attempt to deal 

 in this manner with ticks, a somewhat repulsive group of 

 arachnids which has attracted the special attention of but 

 few professed naturalists, and of which the literature, 

 though considerable in bulk, is extremely scattered, and 

 much of it inaccessible. Consequently, experts on this 

 group have been rare, and the identification of a species 

 has often been a matter of extreme difficulty. 



The main results of the labours of Prof. Nuttall and 

 his colleagues will be to collect together all references to 

 works dealing with ticks, and to give accurate descrip- 

 tions, accompanied with illustrations, of every valid species 

 of tick in such a way that it will be possible for anyone 

 in any part of the world to identify a tick, of a species 

 already known, by aid of this monograph. The under- 

 taking is therefore one which, if successfully carried out, 

 will fill a great gap and render an important service. 



The first two instalments of the monograph are before 

 us. Part i. contains the bibliography of ticks, which 

 covers 68 quarto pages of references. The bibliography is 

 printed only on one side of the paper, so that those who 

 wish to keep it up to date can cut it up and make a card- 

 catalogue of it. Part ii. contains two sections, the first 

 dealing with the classifications of ticks, the second with 

 the genus Ixodes, Latreille, 1795, of which fifty-one valid 

 species are recognised. Following the descriptions of these 

 species, of which all but two are accompanied by illustra- 

 tions, are notes on the geographical distribution, on 

 doubtful species, and on the biology of Ixodes, and a 

 synonymic list of condemned and doubtful species, together 

 with a list of the collections in which the types are to be 

 found. 



A detailed criticism of this work could only be under- 

 taken by an expert writing for experts. We note, how- 

 ever, that the bibliography seems to contain a great many 

 references to works, ancient and modern, which are little 

 more than literary curiosities, and it would, we think, 

 have been useful to separate the chaff from the wheat by 

 indicating in some way those references which advance the 

 scientific knowledge of the group and are to be taken 

 seriously. For our part, we are sceptical as to the utility, 

 in a work of this kind, of references to the opinions of 

 Aristotle, Pliny, and Moses. The fact that the ancients 

 believed ticks to be without an anal aperture may be an 

 interesting " tit-bit," but it is not of much value, scientific 

 or practical, to those who wish to study ticks at the present 

 day. The illustrations are good and very clear, and the 

 work seems singularly free from misprints. Prof. Nuttall 

 has a curious fancy for using inverted commas, in some 

 cases not for quotations, apparently, but for familiar ex- 

 pressions, such as " rattled like peas " or " put in the 

 way of finding their food "; if these are quotations we do 

 not recognise them, nor are we put in the way of finding 

 their source. 



A work of this kind tends, by aiding investigation and 

 discovery, to hasten the advent of the period when it will 

 itself be out of date. It makes it easy for anyone to 

 collect ticks, to identify them, and to discover and describe 

 new species ; hence long before it is completed it will prob- 

 ably require supplements. The study of these parasites, 

 interesting not only to the practical man, but also to the 

 naturalist, as remarkable instances of adaptation to a 

 mode of life which is peculiar, if to ourselves unpleasant, 

 will be greatlv advanced by the publication of this mono- 

 graph ; and both classes of investigators will owe a debt 

 of gratitude to the labours of Prof. Nuttall and his 

 collaborators for raising the scientific knowledge of ticks 

 to a plane in which rapid progress is rendered possible in 

 the future. 



NO. 2195, VOL. 881 



SEISMOLOGY AT THE BRITISH 

 ASSOCIATION. 



w 



E have before us the sixteenth report of the Seismo- 

 logical Committee of the British Association. Th"' 

 may be reasons why this particular report should be 1; 

 as No. 16, but for those interested in seismological ;• : 

 ture such a title may be misleading. As a matter of fat 

 this association has published fifty-two annual report - 

 about earthquakes, some of which, like those by th' 

 Robert Mallet, are reference works for all who are sf 

 of seismology. I direct attention to this matter . 

 indication that Great Britain has not been behind 

 vestigations relating to earth physics. In certain - ; 

 tions it is far in advance of many others. 



The first fact to be gathered from this report is that 

 British Association, in its endeavour to make a seismi 

 survey of the world, enjoy the cooperation of about sixl; 

 stations, which are fairly evenly distributed over t^ 

 surface of our earth. It is remarkable to note that colonia 

 Governments, and particularly cable companies, ha\ 

 established observing stations on many oceanic islands, 

 for example, at Cape Verde, Ascension, St. Heleni 

 Fernando Noronha, Mauritius, Seychelles, Cocos, Fiji, at 

 other places. On March 28 this year the Legislatr 

 Council of Bermuda passed a " Seismographic .Act ' 

 enabling the Board of Public Works to purchase and mail 

 tain instruments for recording earthquakes. Other cr-^-^'^'^f 

 Governments have taken similar steps; whilst the F 

 Government gives direct assistance to an Intern.^ 

 Association which has its headquarters at Strassburg. .An 

 item of considerable interest in the report refers to Double 

 and Multiple Earthquakes, about which we read the 

 following : — 



" Attention has frequently been drawn to the fact that 

 an earthquake as it radiates may cause a collapse of strata 

 which is in an unstable condition, and thus give rise to 

 one or more secondary disturbances. The great earth- 

 quake of Lisbon in 1755 gave rise to secondary shocks in 

 England, Ireland, and probably in many other countries. 

 In the volume containing Physical Observations made in, 

 the Antarctic Regions in 1902-3, published under the super 

 intendence of the Royal Society, p. 92, I gave illustration 

 of secondary earthquakes the genesis of which corresponde 

 in time with the arrival of two particular phases of primar 

 disturbances. That the third phase or the large waves 

 a seismic disturbance as they travel round the worl 

 causing the crust of the same to rise and fall like a rai 

 on an ocean swell, should give rise to one or mc 

 secondary disturbances is not surprising. Farther tha 

 this, any of the latter which may be greater or less tha 

 their parent may in turn become the originator of farth^ 

 settlements. One mcgaseism may therefore cause a reli 

 of seismic strain throughout the world." 



Of multiple earthquakes a number of illustrations 

 given. If the interpretation put upon them is correct, 

 means not only a help to those who wish to analyi 

 seismograms, but a considerable advance in our knowle " 

 of what is taking place beneath our feet. A shake in or 

 place means a shake in many, and it may be added tli 

 the foci of these are probably in that region where cooKil 

 is taking place most rapidly. 



In another section of the report we read about 

 " Synchronism of seismic activity in different regions. 

 For example, it is found that during the last 300 years tt 

 times of activity in Italy, although separated from eac 

 other by irregular intervals, have varied between five ar 

 twenty years, and that these dates of activity in Eurc 

 closely corresponded with dates when there had 

 marked activity in Japan. 



Under a section headed " Megaseismic Frequency ' 

 see that between the years 1899 and 1909 there had 

 508 world-shaking disturbances in winter months and 

 in summer months, which practically means that there 

 as many large earthquakes at one period of the year as 

 any other. 



in connection with seismological work, measuremeJ 

 have been made of the deflection of the vertical by 

 tidal load of the Solent. At Ryde, close to the sea fror 

 it was found that a lo-foot tide caused a deflection 



