NATURE 



\Scpt. lo, 1874 



it woukl be impossible for them lo fall into their present position ; 

 yet we know from their position that the boulders were dropped 

 there before any portion of the screes had accumulated, and 

 therefore at a time when the roof of the cave undoubtedly reached 

 much further forward. 



The inevitable conclusion is that man lived in Yorkshire with 

 Elephas antiqtins, Rhinoceros tichorimis, Ursus priscus and 

 spchms, Hyana, Bison, and red deer long before the existence of 

 the great ice-sheet in Northern Britain and Ireland. 



Report of Ihe Boulder CoDuiiitlee. 



The Rev. W. H. Crosskey read the report of this committee 

 appointed for the purpo._e of recording the position, height above 

 the sen, lithological characters, size, and origin of the mote 

 important erratic blocks, and groups of erratic blocks, of England 

 and Wales, and reporting other matters of interest connected 

 with thiin. A schedule has been issued by the committee 

 containing detailed questions of the information required. The 

 obiect of the committee is not speculative, but to collect the 

 facts, with the intention of afterwards proceeding to their classi- 

 ficatijri, and pointing out their relations to the various theories 

 ur oer designation in glacial geology. Dislricts in which boulders 

 are rarest are of special importance. The evidence regarding 

 the southward extension of the ice sheet and the reach of the 

 waers of tlie glacial sea depends largely upon their presence and 

 absence ; while their method of distribution is full of geological 

 niean-ng. The necessity for the work of the committee is in- 

 cea-ed by the fact that aF over England and Wales the destruc- 

 tion of boulders is rapidly proceeding. In the midland districts, 

 a map is being constructed in which the approximate number of 

 boulders and the character of the rocks of which they are formed, 

 together with the effect of the configuration of the country on 

 their distribution, will be shown. From the general position of 

 the boulders it is evident that boulders were deposited at several 

 ages. There are (i) boulders of the earliest ice periods, (2) 

 boulders of the period of submergence, distributed in the lower 

 parts of the glacial clays, (3) boulders of the period of the re- 

 elevation of the land. These varieties have yet to be traced to 

 their various sources, and upon this work members of the 

 committee are engaged. It is as impossible to assign all the 

 lioulders to one epoch of distribution, as it is to relegate all 

 glacial sands, clays, and gravels to one period. The report 

 contains details regarding boulders of various districts. From 

 Leicestershire, one tact of especial importance is recorded. Below 

 the drift clay and quite distinct from the surface boulders freely 

 scattered over the country, a group of boulders has been exposed 

 in an excavation made in the centre of Leicester, 25 ft. deep, 

 composed of rocks of foreign orit;in, and suggesting a stranded 

 iceberg of an early period. In the same county, isolated 

 boulders of large size, and groups traceable to sources some miles 

 distant, prove Chainwood Forest to have been a centre of ice- 

 action of considerable intensity. In Warwickshiie a great 

 thaiige occurs. The drift-beds aie reduced almost to pebbles ; 

 rnd local geologists give the name of boulders to specimens 

 which in other parts would not be regarded as worthy of the 

 i.ame. Striations are faint and rare. Their grouping is remark- 

 able, and they come from all points of the compass. Isolated 

 1 oulders are recorded from IJorthumberland, Yorkshire, Lanca- 

 shire, Devonshire, and Denbighshire. The committee request 

 members of the Association who have received schedules to re- 

 turn them, and desire communications from geologists disposed 

 10 assist them in their work. 

 T/ie Close Time Connnittce. 



A report was read from the Close Time ConimiUee with refer- 

 mce to the desirableness of establishing a close time for the pre- 

 servation of indigenous animals. After stating the steps which 

 1 ad been taken with reference to this subject in Parliament, the 

 committee stated its belief that the effect of birds' nesting on 

 .such kinds ol birds as are known to be diminishing is altogether 

 inappreciable, while its effect on ihose whose numbers are not 

 decreasing may he safely disregarded, and consequently that tlere 

 is no need of ary legislative mteiference with the practice. The 

 committee believed that the only practicable mode of checking 

 the diminution of such birds as have been proved to be decreas- 

 ing is Ihe tfleclual piotection of the adults from destruction 

 curing the bleeding season. While the Sea Birds Prtservation 

 Act continued to woik successfully, the Wild Birds Biotection 

 Act had done little, if anylh.ng, towards aitaining the objects 



■ r whith it was yasstd, and in various quarters gave considcr- 

 :i]e discontent. Bin's con n.only kn<Avn as "wild fowl" were 

 >Mtie>lid 10 very guat j fisicutiin tbri.i.gh Ihe inadequacy of 



the present law to protect tliera ; they were rapidly reducing in 

 number ; they were not only innocuous, but were of great value 

 as food. Consequently the committee hoped that the efforts 

 they intended to make on behalf of wild fowl in tlie next session 

 of Parliament would obtain a general support:. Representations 

 as to the inordinate slaughter of seals w-hich took place eveiy 

 spring in the North Atlantic Ocean had been made to some 

 members of the committee. There could be no doubt that such 

 slaughter at that season would soon bring these animals to the 

 verge of extermination, as had been the case in many other ])arts 

 of the world, and since their destruction would affect a very large 

 trade, their proper protection seemed to be a subject not at all 

 unworthy of Ihe consideration of the Government. The com- 

 mittee requested their reappointment. 



SECTIONAL PROCEEDINGS 



SECTION A— Mathematics 



Oit the Perliirhalions of the Compass produced ly the rolling of 

 the Ship, by Sir William Thomson. 



The heeling error which has been investigated by Airy and 

 Archibald Smith is the deviation of a compass produced by a 

 " steady heel " (as a constant inclination of the ship round a 

 longitudinal axis, approximately horizontal is called). It depends 

 on a horizontal component of the ship's magnetic force, in- 

 troduced by the inclination ; which compounded with the 

 horizontal component existing when the ship is upright, gives 

 the altered horizontal component when the ship is inclined. 

 Regarding only the error of direction and disregarding the change 

 of the intensity of the directing force, we may define the heeling 

 error as the angle between the directions, for the ship upright 

 and for the ship inclined, of the resultant of the horizontal mag- 

 netic forces of earth and ship at the position ol the compass. 

 These suppositions would be rigorously realised with the compass 

 supported on a point in the ordinal y manner if the bearing point 

 were carried by the ship uniformly in a straight line. They are 

 nearly enough realised in a large ship to render inconsiderable 

 the errors due to want of perfect uniformity of the motion of the 

 bearing point if this point is placed anywhere in the "axis of 

 rolhng," * for in a large ship the compass, however placed, is 

 not considerably disturbed by pitching, or by the inequalities of 

 the translatory motion caused by waves. 



Hence, supposing the compass placed in the axis of rolling, 

 the perturbation produced in it by the rolling will be solely that 

 due to the variation of the horizontal component of the ship's 

 magnetic force. Such a position of the compass would liave one 

 great advantage — that the application of proper magnetic cor- 

 rectors adjusted by trial to do away with the rolling error would 

 perfectly correct the heeling error. To set off against this 

 advantage there are two practical disadvantages : one that the axis 

 of rolling (being always below deck) woula not be a convenient 

 position tor the ordinary modes of using the compass ; the other, 

 Jar more serious, that in ships, at all events with iron decks, the 

 magnetic disturbance produced by the iron of the ship would 

 probably be so much greater at any point of the axis of rolling 

 than at suitably chosen positions above deck as to more than 

 counterbalance the grand kinetic advantage of the axial position. 

 But careful trials in ships of various classes ought to be made, 

 and it tnay be found that in some cases the compass may with 

 preponderating advantage be placed at the axis of rolling. 

 Hitherto, however, this position for the compass has not been 

 used in ships of any class, and, as we have seen, it is not pro- 

 bable that it can ever be generally adopteil for ships of all 

 classes. It is therefore an interesting and impoilant piactical 

 problem to determine the perturbations of the compass produced 

 by oscillations or other non-uniform motions of the bearing 

 point. 



The general kinetic problem of the compass is to determine 

 the position at any instant of a rigid body, consisting of the 

 needles, framework, and fly card, which for brevity will be 

 called simply the compass, moveable on a bearing point, when 

 this point moves w-ith any given motion. Let the bearing point 

 experience! at any instant a given acceleration, a, in any given 

 direction. Let 70 be the mass (or weight) of the compass, and 

 ^ w the force of gravity upon it, reckoned in kinetic units. The 



* One way, probably the best in practice, of finding by observation the 

 position of the axis of rolling is to hang peiidnlnms from points at different 

 levels in the plane through the heel perpendicnlar to the deck, till one is 

 foni'd which indicates the same degrees ol rolling as tho-e found geometri- 

 cally by observing a graduated scale (or " baiten '') seen against the 



