246 



NATURE 



{July II, 1889 



we are staying in Canea, leaving home early in the morning. 

 lie presented the bird to one of the children in the house, and 

 it was put in a cage and hung at the window, where it seemed 

 likely to be contented, losing its fright after a few hours. Late 

 in the afternoon an old bird was noticed fluttering about the 

 cage apparently trying to get at the little one, and the young 

 bird on its appearance became frantic to get out to the old one. 

 It was evidently the mother of the young one, as the recognition 

 was too cordial to have been owing to the interest of a strange 

 bird ; and when my daughter opened the cage, as she did after a 

 little, they both flew off rapidly in tbe direction of Zukaleria. 

 It is impossible that the old bird should have followed the 

 gardener, as we should have seen it earlier in the day. 



Canea, Crete, June 27. W. J. Stillman. 



Seismology in Italy. 



I HAVE only lately seen Dr. Johnston-Lavis's article in 

 Nature (vol. xxxix. p. 329), on the present state of seismology 

 in Italy. I have read it with much interest, and with the 

 greatest satisfaction, because it deals with the most recent works 

 due to the new and serious impulse given to the study by the 

 Government during the last five years. I thank the author for 

 having noticed one of my writings, " Sulla sistemazione delle 

 osservazioni geodinamiche regolari." There is little — hardly 

 anything— absolutely new in this work, because in writing it I 

 desired only to sum up the deliberations of the Royal Geody- 

 namical Commission, to which I had the honour to belong. I also 

 brought together in it all that was really serious and positive in 

 other works, with the intention of dispelling the confusion 

 which unhappily prevailed when this scientific branch was in the 

 power of dilettantism, which had the prerogative of the long- 

 winded style, the charlatanism, and the seismic magic, of which 

 the author of the article justly complains. In a word, I wished 

 to set forth a proper programme, with the ideas which the 

 Commission conceived, and which continue to form the principle 

 of the deliberations of the directing Council for Meteorology and 

 Geodynamics, in which the Commission has been merged On 

 this serious and well-determined principle the service is continued 

 in the island of Ischia as elsewhere. 



In accordance with the just ideas of your correspondent, I 

 must nevertheless make one remark on the subjects which relate 

 more especially to the studies carried on in the island of Ischia ; 

 namely, that there is really something of novelty in some of the 

 other writings of mine included in the volume that contains the 

 work commented on. 



One of these writings consisted of the theoretical relation I 

 presented in response to the demand of the Royal Geodynamical 

 Commission in the sittings of June 1886. The approval of this 

 work by the Commission contributed to the adoption, for the 

 study of the form of seismic movements, of the mechanical 

 principle of three components adapted to a steady point. This 

 principle was studied, and put into execution, by the mechani- 

 cians Brassart of the Central Office of Meteorology and Geody- 

 namics ; and while it has tended to simplify completely the 

 methods used in the observation of earthquakes, and to bring to 

 an end the innumerable imperfections of former times, it is not 

 even yet well understood by men of the old school. 



Three of my works relate to the variations observed in the 

 temperature of the thermal springs at Porto d' Ischia. A 

 rigorously mathematical analysis has revealed a hydrostatical 

 law in relation to changes in the level of the sea. Later studies 

 which I rmdertook upon the diagrams of a registering thermo- 

 meter, and which the Director, Prof. Tacchini, presented to the 

 Accademia dei Lincei on October 7, 1888, proved the in- 

 fluence exerted by the horary state of ihe tide, while previously 

 some isolated observations had made way for hypotheses of 

 another nature. 



Another of my works expounds a new principle for rendering 

 astatic — or nearly so — in a horizontal direction, the steady point 

 in seismographs, and gives a mathematical demonstration of it. 

 Upon this principle, which I conceived in 1886, is apparently 

 based the construction of an instrument by Prof. Ames (see the 

 American Jotiriial of Science, February 1888, p. 106) ; but the 

 fact that he has made the suspension with four threads, instead of 

 three, suffices to prove that he has not farmed a precise idea of 

 my original principle, and that he has much less considered it 

 ^ necessary to procure for himself the mathematical proof of it. 

 Some months before the publication of Mr. Ames's work I took 



care to bring out prominently, on p. 266 of the volume referred 

 to, the error to which one would expose oneself in this way. 



Of the ten writings by me in the volume, these are the works 

 to which I attach some importance ; and I take the liberty of 

 directing to them the attention of your readers, in the hope of 

 making known the beginnings of the success which is to be 

 achieved through the action of the Italian Government. For 

 the rest, the history of this enterprise is set forth in the abstract 

 of the sittings which forms the introduction of the volume. 

 GiULio Gkablovitz, 

 Director of the Osservatorio Geodinamico 

 di Casamicciola. 



Saxicava Borings and Valves in a Boulder Clay Erratic. 



When examinin_:i a few weeks ago the boulders in the workings 

 of the New Ferry I3rick and Tile Company, Cheshire, with Mr. 

 Harnett Harrisson, we discovered a boulder having superficially a 

 scoriaceous appearance, which on examination proved to be 

 of limestone, and perforated with Saxicava and other borings. 

 After careful washing several of the burrows were found to be 

 occupied by the shells of the animal that had made them, both 

 valves complete. The washings that came out of the burrows 

 after careful reduction by pouring off the clay water I found to 

 consist of well-rounded grains of quartz intermixed with a few 

 microscopic drift pebbles and small shell fragments. Some of 

 them were very much rounded and waterworn. Several broken 

 spines of Echinus also occurred. 



The stone was taken from a heap picked out of the boulder clay 

 previous to passing it through the machine. There is no doubt as 

 to its origin, as one side is strongly planed and striated in the 

 direction of the longer axis. The extreme measurements are 

 6i" X 4J" X 2|"; weight, 3 lbs. 10 oz. The Saxicava burrows are 

 placed so as to give the idea that the stone had lain on the 

 glaciated side when most of them were made, as they get nearly 

 horizontal towards the glaciated bottom. The termination of 

 one burrow, however, occurs on the planed face. There are alsa 

 other worm-like burrows which occur on the glaciated face, and 

 one of them has been cut longitudinally for a length of an inch 

 by the plane of glaciation. 



It is now about eighteen years since I commenced a study of 

 the glacial deposits of the north-west of England, but have 

 never found a similar example with the burrows occupied, 

 although the low-level boulder clay in which it occurs is almost 

 universally more or less full of shell fragments. The bearing of 

 the discovery on the origin of the low-level boulder clay is 

 obvious. 



The history of the stone appears to have been this. It had its 

 origin in the Carboniferous limestone of the north ; it has then 

 been rounded into a boulder, has lain upon a shore, and become 

 the seat of operations of molluscan and other burrowers. After- 

 wards it has been frozen into coast-ice, glaciated by attrition on a 

 pebbly or rocky shore through tidal movement, has been again 

 released from the ice grip, spent another tine on the shore resting 

 on its glaciated face, during which period it became perforated 

 with the Saxicava burrows now occupied by the remains of the 

 animal. While still on the shore, fragments of shells of other 

 Mollusca got washed into the occupied and unoccupied perfora- 

 tions, and finally it was again frozen into coast-ice, floated off, 

 and dropped into the bed of the low-level boulder clay sea, 

 where it remained undisturbed until the pick of the brickmaker 

 disinterred it. The boulder clay in which it occurs is plastic, 

 and lontains comparatively few stones, and there are no sand 

 seams to be seen in the present face, though I believe they 

 occur at a greater depth below the bottom of the pit. 



The special interest of this example lies in the proof it affords 

 of the marine origin of the low-level boulder clay of Cheshire 

 and Lancashire. Some geologists contend that this clay is the 

 bottom of the Irish Sea ploughed up by land ice, but the 

 necessities of a theory that requires such an operation to have 

 taken place in the past when there is an obvious and simple 

 explanation at hand does not commend it to my mind. It is not 

 even proved that such a ploughing up is passible ; no examples are 

 adduced where such a phenomenon is going on ; it does not 

 account for the structure of the beds of low-level boulder clay ; 

 and speaking from eighteen years of close investigation, there is 

 no necessity in the nature of the case for resorting to such an 

 extreme hypothesis. 



The age of land ice preceded that of the low-level marine 



