192 



NATURE 



[June 20, 1901 



at low altitudes. A fourth source of error, in the adjustment 

 of the polar axis, must be also considered, and it is practically 

 important to do this, inasmuch that by an accurate knowledge 

 of the conditions it is possible to introduce such an amount of 

 error from this and the clock rate as to partially eliminate the 

 variable errors due to flexure, &c. After insisting on the 

 necessity of the clock having as continuous and regular motion 

 as possible, it is pointed out that the correct rate for following 

 is not sidereal time, as is commonly supposed, but a varia- 

 tion from this depending on the latitude and the declination 

 of the object. The equations of condition are developed for 

 determining the proper following rates for various localities. 

 The actual path of a star on the plate as affected by refraction 

 may be either a parabola, hyperbola, ellipse or circle. The 

 effect of error of the polar a.\is is an elliptical form of star 

 image, varying with the declination. The analytical in- 

 vestigation of this shows that the refraction in declination can 

 to a great extent be eliminated by an alteration of the in- 

 clination of the axis ; this is now provided for in many instru- 

 ments by the frequent shifting of the polar axis by known amounts. 

 The correction for the right ascension component is more com- 

 plicated, and tables are given showing the changes per hour 

 for various hour angles. Reproductions from photographs 

 taken with clock rate adjusted for refraction and polar axis 

 elevated are shown. In considering the effects of flexure 

 three kinds are discussed, affecting either the polar or declin- 

 ation axes, and the tube. Various methods actually in use at the 

 Observatory for determining the flexure are then described in 

 detail, also the exact method of varying the load of the control 

 pendulum governing the driving clock. The effects of tem- 

 perature on the trails have also been considered, and methods for 

 its elimination. 



As the result of the investigation, it is found that plates of 

 60 minutes' exposure may be taken without visual following, 

 which shall have images not exceeding O'oi cm. in elongation 

 due to the clock, and a photograph of the cluster in Hercules 

 taken in this way is reproduced. Several special applications 

 of these principles are then discussed, including the important 

 one of photographing stellar spectra with the objective prism, 

 where the spectrum lines are often very oblique, thus lessening 

 the dispersion and possibly the definition. A table is calculated 

 showing that this may be corrected by a slight rotation of the 

 prism for each star. 



Several methods for the mechanical correction of flexure 

 are indicated, and finally ' the special means for correcting 

 proper motions of the object under examination are con- 

 sidered, examples of the photographs of Eros being given in 

 illustration. 



THE SIXTH ANNUAL CONGRESS OF THE 

 SOUTH-EASTERN UNION OF SCIENTIFIC 

 SOCIETIES. 

 T^HIS Congress was held at Haslemere and Hindhead on 

 June 5-S, and delegates and members representative of 

 most of the affiliated societies upon the Union's list were in 

 attendance. There were, further, a goodly number of visitors 

 present, attracted to a large extent by the unbounded hospitality 

 of the residents and admirable arrangements of the local com- 

 mittee, which were most elaborate and highly successful. 



The proceedings were opened by Prof. G. B. Howes, F.R.S., 

 who, as the retiring president, in a few apposite remarks resigned 

 the chair to his successor, Mr. G. A. Boulenger, F. R.S., who 

 then deUvered the annual address. Taking for his subject the 

 field-work and results of experiment of the past quarter of a 

 century upon the European Keptilia and Batrachia, he led up 

 to the formulation of a revised list of the British species. He 

 then dealt in greater detail with those genera and species 

 inhabiting the immediate neighbourhood of the meeting, special 

 interest attaching to some facts involving the natterjack and 

 Gilbert White's area of observation, in their relation to the topic 

 of batrachian migration ; and he seized the opportunity to enlist 

 the services of local naturalists in the study of this problem, in 

 the better working-out of the varieties of the common viper, 

 and in other allied herpetological matters for which the study of 

 the local fauna presents a favourable opportunity. Beyond this 

 the address, which was admirably suited to the occasion, con- 

 tained historical records of permanent value and some whole- 



NO. 165 1, VOL. 64] 



some advice to the collector and would-be specialist, based upon 

 the author's great experience of herpetological affairs. 



The meetings for strictly scientific business were confined to 

 the Friday and Saturday mornings, five papers being read. An 

 unusual departure, however, was entered upon, in the substitu- 

 tion of three short addresses for the musical entertainment cus- 

 tomary on similar occasions at the evening soirh. The reception 

 at this was by Sir F. Pollock, Bart., and in his capacity as 

 president of the local natural history society he delighted those 

 present with a felicitous speech. The short addresses which 

 followed this were by Mr. G. F. Chambers, on " An Eclipse 

 Trip to Portugal in 1900" ; by Mr. Oswald Latter, of the 

 Charterhouse, on "Cuckoos' Eggs"; and by Dr. Jonathan 

 Hutchinson, F. R. S., on "Habit and Discipline in their 

 Influence on Organisation." The latter, on the lines of the 

 famous Sunday afternoon discourses with which the indefatigable 

 doctor is in the habit of improving the minds of his friends and 

 visitors, both at Haslemere and in London, w.as noteworthy for 

 the attempt to prove that the orbital bulla of the hippopotamus, 

 shown to be different in origin in each of its two stages of de- 

 velopment, is, like that of the gavial, functional as a support for 

 the eye during protraction and elevation ; and for the thesis that 

 in human affairs the poet must precede the philosopher. 



Dr. Hutchinson further contributed to the educational success 

 of the meeting by entertaining the assembled guests at his private 

 museum at College Hill, the originality of the plan of arrange- 

 ment of which was much admired ; and, with characteristic 

 versatility, he followed this up by leading the way to Lord 

 Tennyson's abode at Blackdown, before which, after a visit to 

 its interior, verses appropriate to the occasion were by him and 

 others recited. 



Of the papers read at the ordinary meetings, the first, by the 

 Hon. Rollo Russell, on " Moisture in the Atmosphere," is the 

 embodiment of a lengthy series of experimental and statistical 

 observations which will be of much service for reference. This 

 was followed by a paper by Miss E. Sargent on " Seedlings," 

 chiefly noteworthy for some observations made in conjunction 

 with "a colleague," in which a downward displacement of the 

 seed by forcible contraction of the roots was fully described 

 and illustrated by an ingenious model. Prof. Howes concluded 

 the first morning's work with a short lecture, which he said was 

 pertinent to his presidential address of the previous year. He 

 dealt with the principle of " convergence," as applying more 

 especially to recent work among the Mammalia and Batrachia 

 ecatidata, and with "substitution" in its bearings on the study 

 of the electrical organs of fishes. 



The afternoon of Friday was given to the reading of a couple 

 of papers on "The Teaching of Nature Knowledge in Ele- 

 mentary Schools," by Miss M, A. Buckton, who has had con- 

 siderable experience of elementary school-work both on the 

 Continent and at home, and by Prof A. D. Hall, principal of 

 the Wye Agricultural College. Upon these a discussion arose, 

 which, for lack of organisation beforehand and time for exten- 

 sion, fell short of what might have been an important issue. 



The concluding paper of the meeting was by Mr. S. T. Dunn, 

 secretary to the Director of Kew Gardens, under title "The 

 Origin of Certain Weeds." The author read an account of the 

 geographical distribution of certain dead nettles, and in the 

 short discussion which ensued doubt was expressed whether he 

 had pointed to anything which does not apply to certain other 

 British plants well known, while there arose a difference of 

 opinion which left the audience in uncertainty as to what 

 constitutes a " weed." 



At the meeting of delegates, which closed the proceedings, 

 the question of subscription was discussed ; and conspicuous 

 among the motions passed was one of appeal to the Brighton 

 Town Council, who are about to take the famous Aquarium of 

 that town in hand for development, to make adequate provision 

 for scientific investigation and work in economics, in a manner 

 which was agreed upon. 



The e.\quisite country in which the meeting was held and the 

 delightful weather which prevailed proved both beneficial and 

 attractive, and not the least pleasurable feature of the Congress 

 was the manner in which the influential residents, both by their 

 generous hospitality and personal interest, contributed to its 

 success, while the vociferous croaking of some introduced frogs 

 came as a most appropriate accompaniment to the proceedings. 



The Congress for 1902 is to be held at Canterbury, under 

 the presidency of Dr. Jonathan Hutchinson, F. R.S., who has 

 served the recent one so well. 



