476 



NATURE 



\Sept 28, 1876 



able instance of self-fertilisation occurs in R. aboriivus, 

 whose petals do not close at night. It seeds profusely, 

 yet is wholly neglected by insects, notwithstanding that it 

 possesses large nectariferous glands. Instead of the flower 

 closing, the slender pedicels droop at night, inverting the 

 flower, and thus allowing the pollen to fall from the petals, 

 on which it is shed, upon the stigmas. Mr. Meehan con- 

 cludes that some deeper purpose than has yet been con- 

 ceived governs the fertilisation of plants. In view of 

 these examples, nature cannot "abhor" in-and-in-breed- 

 ing, and it can hardly be that colour, fragrance, and 

 honeyed secretion in flowers have been developed solely to 

 secure cross-fertilisation. Evolutionists will await with 

 interest further researches by Mr. Meehan, and confirma- 

 tory evidences from other inquirers. 



THE BRITISH ASSOCIATION 

 REPORTS 



Mr. Chrystal read the following summary of a Report upon a 

 Comparison of the B, A. Units of Electrical Resistance \hi.\.h2t.A. 

 been performedby himself and Mr. S. A. Saunder. — The experi- 

 ments, of which I have here an account, were undertaken for the 

 purpose of comparing the British Association Standards of Resist- 

 ance now deposited in the Cavendish Laboratory at Cambridge. 

 In the account of the work Mr. Saunder and myself have en- 

 deavoured as much as possible to enable anyone who consults 

 it to judge by internal evidence of the accuracy of the comparison. 



The experiments were so arranged as to give a check on their 

 own accuracy. 



In work of this kind the limit of accuracy is much sooner 

 reached in the temperature than in the electrical measurements. 

 It is to them therefore to which the greatest attention has to be 

 given. 



We took advantage of an extremely convenient source of nearly 

 constant temperature in the tap-water of our experimenting room, 

 which we found by careful observation to remain constant within 

 the tenth of a degree centigrade for a sufficiently long time. By 

 means of this we could find the differences between the resistances 

 of the several coils at temperatures all near 10° C. The method 

 used for obtaining these differences was a very convenient one, 

 described by Prof. Carey Foster in the October number of the 

 Journal of the Society of Telegraph Engineers for 1874. 



To obtain the co-efficients of resistance-temperature variations 

 it was necessary to make resistance measurements at a higher 

 temperature. The temperature chosen was 16° C. 



The coils were brought to this temperature by careful nursing 

 for an hour or more. 



The results of these experiments combined with those at the 

 lower temperature gave the variation co-efficients. The differences 

 at any given temperature coidd then be calculated. 



Lastly, a series of direct comparisons were made, and the 

 result compared with calculation in order to get an idea of the 

 accuracy of our work. 



There is a difficulty in giving a comparison between our results 

 and those of the last measurements given in the British Associa- 

 tion Report on Electrical Standards. This arises from a want 

 of definite information about these last measurements. 



Unfortunately on most of the coils the brass labels have never 

 been completed as was intended, and although we think we 

 managed to identify the coils described in the report with one 

 exception, yet still more definite information is desirable. It is 

 because we have felt this want that we have made our own 

 report more minute than might otherwise have seemed necessary. 



We hope that no ambiguity will exist when the coils are 

 compared again either now to check our results or some ten 

 years hereafter to find whether the standards have varied relatively 

 to each other. 



With this caution I give a series of temperatures at which the 

 standards are equal to each other according to our measurements 

 side by side with one of the temperatures given in the report. 



Last found. B.A. Report. 

 LPt.Ir. 2 i6-i i6-o 



3 I5"8 15-8 



Au.Ag. 58 ... 15-3 15-3 



i^t. 35 i6-o 157 



.. 36 15-8 157 



PtAg. 29 i8-2 15-2 



We have laid these measurements before the British Association 

 in the hope that they will be found useful and be made accessible 

 to those interested in such matters. 



Report of the Committee for effecting the Determination of the 

 Mechanical Equivalent oj Heat. — Progress has been made with 

 the experiments undertaken by Dr. Joule on behalf of the Com- 

 mittee. Friction of water is the method employed, and the 

 average result of upwards of sixty experiments is 772*2 in British 

 gravitation units at Manchester. The greatest deviation from 

 the above average is Tj^iy. 



Experiments have yet to be made on the capacity for heat of 

 the brass of which the calorimeter is constructed, which has pro- 

 visionally been calculated from the results of Regnault for this 

 alloy. The greatest possible error which may have arisen in 

 this way is believed to be ^J^th. Dr. Joule also proposes to 

 compare his mercurial thermometers with the air thermometer 

 with a view to obtain accurate boiling points, and thus correct 

 values of the thermometric scale. The greatest correction which 

 it may be found needful to apply on this account amounts to 

 about TTcth. These maximum corrections, if taken in the same 

 direction, would necessitate the addition or subtraction of 4*5 

 from the equivalent above named. The experiments made by 

 Him on the friction of water have led him to the number 786; 

 but the average of his results, derived from the friction, boring, 

 and crushing of metals, gives 774. 



Assuming that the above experiments and those made by Dr. 

 Joule for the Committee on Standards of Electrical Resistance 

 are to be relied on, the unit issued by it would appear to have 

 a resistance one-fortieth too small. Inasmuch as the locality 

 in which the experiments for that unit were conducted was 

 open to objection, it appears desirable that they should be 

 conducted under more favourable circumstances. 



Report of the Committee on the Distribution of Erratic BouU 

 ders. Read by the Rev. H. W. Crosskey, M.A. — One hundred 

 and sixty-five additional erratics have been catalogued west and 

 south-west of Birmingham, of which 105 have travelled from 

 considerable distances. West and south-west of the midland 

 table-land a large proportion of the blocks are portions of highly 

 indurated ash-beds. To the north and west granite is much 

 more abundant. 



Between the 400 and 500 ft. contour lines at Bothel (North 

 Cumberland) is a large block which has been transported from the 

 north-west portion of Dumfriesshire, about forty miles from 

 N.N.W. to S.S.E. Fragments of Shap Fell Granite occur near 

 Dufton (Westmoreland), 800 feet above the sea-level. The east 

 and north-east boundary of the Arenig dispersion may be roughly 

 defined as extending from Chirk by Cefn, Ruabon, Wrexham, 

 Caergwile, Mold, and the east side of Halkin Mountain to 

 Holywell, and thence in a westerly direction to the Vale of 

 Clwyd. This line nearly coincides with the boundary of the 

 great Northern Granite drift. The Welsh and the northern 

 drifts have to a slight extent crossed the average boundary, and 

 a few Arenig boulders have crossed the estuary of the Dee into 

 the peninsula of Wirral, where they become mixed with the 

 very abundant northern drift from the Lake district and the 

 south of Scotland. The felspathic blocks from the Arenig 

 range have radiated to great distances over an area extend- 

 ing from N.N.E. to E., and to short distances from east to south- 

 east ; and have found their way across valleys and over water- 

 sheds and high mountains. The direction of the glacial striae on 

 rock surfaces in the eastern part of North Wales as well as in the 

 Arenig mountains, agrees in general with the course taken by the 

 boulders. 



The Committee invoke the assistance of geologists in carrying 

 on their investigation. Schedules indicating the particulars 

 required, may be had from the secretary. The rate at which 

 the boulders are disappearing, owing to agricultural and build- 

 ing operations, makes it desirable to register their occcurrence 

 without delay. 



The report of the Close Time Committee gave an account of 

 the steps which led to the passing of Mr. Chaplin's Bill for the 

 Preservation of Wild Fowl last Session, and included a circular 

 extensively distributed by the Committee to further that object. 

 Lord Walsingham, Mr. Chaplin, and Mr. Rodweli were warmly 

 thanked for their exertions in the matter. The Committee 

 thought it possible that something further might be done to 

 regulate the proceedings of bird-catchers ; but the difficulties in 

 the way appear so serious, that immediate success is not ex- 

 pected. The Sea Birds Preservation Act^continues to work satis* 



