Junk 30. 1898] 



NA TURE 



207 



and water supplies, and several local authorities have requested 

 the Institute to undertake this systematic examination on their 

 behalf. Bacteriological work has also been undertaken for 

 several additional sanitary authorities. In the new building 

 •every facility is being provided for the furtherance of bacterio- 

 logical research. The Institute will require, however, a con- 

 siderable addition to its funds to enable it to carry out adequately 

 the objects for which it was founded. 



The preliminary programme of the sixteenth Congress of the 

 Sanitary Institute, to be held in Birmingham, from September 

 27 to October i, has now been issued. The President of the 

 Congress is Sir Joseph Fayrer, Bart., K.C.S.I., F.R.S. Dr. 

 Christopher Childs will deliver the lecture to the Congress, and 

 Dr. Alex Hill, Master of Downing College and Vice-Chancellor 

 of Cambridge University, will deliver the popular lecture. 

 Excursions to places of interest in connection with sanitation 

 will be arranged for those attending the Congress. A conver- 

 sazione will be given by the Right Hon. the Lord Mayor 

 (Councillor C. G. Beale), and a garden party, at the Botanical 

 Gardens, Edgbaston, will be given by members of the Sanitary 

 Committee. It appears from the programme that over three 

 hundred authorities, including several County Councils, have 

 already appointed delegates to the Congress, and, as there are 

 also over two thousand members and associates in the Institute, 

 there will probably be a large attendance in addition to the local 

 members of the Congress. In connection with the Congress, a 

 Health Exhibition of apparatus and appliances relating to 

 health and domestic use will be held as a practical illustration of 

 the application and carrying out of the principles and methods 

 ■discussed at the meetings ; which not only serves this purpose, 

 but also an important one in diffusing sanitary knowledge among 

 a large class who do not attend the other meetings of the Con- 

 gress. The Congress will include three general addresses and 

 lectures. Three Sections will meet for two days each, dealing 

 with (i) Sanitary Science and Preventive Medicine, presided 

 over by Dr. Alfred Hill ; (2) Engineering and Architecture, 

 presided over by Mr. W. Henman ; (3) Physics, Chemistry, 

 and Biology, Dr. G. Sims Woodhead. There will be five 

 special conferences : Municipal Representatives, presided over 

 by Alderman W. Cook ; Medical Officers of Health, presided 

 over by Dr. John C. McVail ; Municipal and County Engineers, 

 presided over by Mr. T. de Courcy Meade ; Sanitary Inspectors, 

 presided over by Mr. W. W. West ; Domestic Hygiene, pre- 

 sided over by Mrs. C. G. Beale (the Lady Mayoress). The 

 local arrangements are in the hands of an influential local 

 Committee, presided over by the Right Hon. the Lord Mayor 

 of Birmingham, with Prof. A. Bostock Hill, Mr. W. Bayley 

 Marshall, and Mr. J. E. Willcox as Honorary Secretaries. 



Dr. G. Vailati, writing in the BoUetino di Storia e Biblio- 

 grafia Matei/iatua, has brought to light an obsolete book of 

 Euclid dealing with balances and the principle of the lever. 

 This work has become known through an Arabic translation by 

 Ibn Musa in the National Library at Paris, an account of which 

 was given in 185 1 by Woepke in the jfotirnal Asiatique, but 

 seems to have been overlooked by mathematicians. Euclid's 

 reasoning is based on the two axioms: (l) that if a loaded lamina 

 balances about a horizontal axis, it will continue to balance when 

 the weights are displaced parallel to the axis ; (2) if a lamina 

 balances horizontally about two intersecting axes in its plane, it 

 will also balance about their point of intersection. From these 

 axioms, Euclid deduces a proposition practically equivalent to a 

 special case of the theorem that three equal weights placed at 

 the vertices of a triangle will balance about a median. Then 

 by the first axiom a second proposition is proved, virtually 

 amounting to the statement that a single weight on one side of 

 a lever will balance two equal weights on the opposite side if 

 NO. 1496, VOL. 58] 



the distance of the first from the fulcrum is equal to the sum of 

 the distances of the second and third. By the superposition of such 

 sets of equilibrating systems, and the removal of pairs of weights 

 symmetrically placed on opposite sides of the fulcrum, Euclid 

 arrives at the conditions of equilibrium on a lever whose arms 

 are in the ratio of two whole numbers by a method closely 

 analogous to that adopted by Archimedes. 



Dr. Adrien Gu^bhard, of St. Vallier-de-Thiey, sends us a 

 number of papers dealing with the supposed photographic re- 

 presentation of currents emanating from the human body, con- 

 cerning which much appears to have been said in France a few 

 months ago, when the subject was brought into prominence by 

 the announced discoveries of Dr. Baraduc and the late Dr. Luys 

 Briefly told, when a slightly fogged photographic plate is de- 

 veloped in a shallow bath, and the experimenter presses his 

 fingers on the plate during the process, streaks are observed to 

 radiate from the parts touched. So far from the effect being 

 due to "animal magnetism," or any of the other occult in- 

 fluences with which spiritualists are wont to deal, Dr. Guebhard 

 shows that the lines are simply caused by convection currents 

 produced by the warmth of the operator's finger. If for the 

 latter there be substituted a small india-rubber ball filled with 

 warm water, exactly the same impressions are produced. 

 Similar results are obtained with a body cooled below the 

 temperature of the developer, and in each case their intensity 

 is greater the greater the difference of temperature. In some 

 of Dr. Guebhard's figures the lines closely resemble the 

 lines of flow due to sources and sinks, or the lines assumed by 

 iron filings in the presence of magnets ; as representations of the 

 lines of flow of convection currents, these figures may interest 

 the physicist. 



We have received a copy of the observations made at the 

 Blue Hill Meteorological Observatory, Massachusetts, during 

 the year 1896, forming Part i. vol. xlii. of the Annals of the 

 Astronomical Observatory of Harvard College, containing 

 results of observations made at three stations as in former 

 years. The primary station is the observatory on the summit 

 of Great Blue Hill, at an elevation of 640 feet above mean 

 sea-level, and the two secondary stations are situated north- 

 west of it, one being at the base of Blue Hill. In addition to 

 the usual meteorological tables and hourly cloud observations 

 and measurements of heights and velocities recommended by 

 the International Meteorological Committee, the work contains 

 an interesting study of special cloud forms and their relations 

 to cyclones and anticyclones, as well as to other phenomena, by 

 A. E. Sweetland. One of the principal features of the work 

 of the observatory is the exploration of the air by means of 

 kites. A full description of the methods employed is given by 

 S. P. Fergusson, and a valuable discussion of the records by 

 H. H. Clayton. This exploration was begun in August 1894, 

 and is, we believe, the most thorough study of the lower strata 

 of free air ever made, and occasionally very high altitudes are 

 also attained. We are glad to see that the continuance of the 

 useful observations at Blue Hill, now maintained by the 

 liberality of Mr. A. L. Rotch, has been assured by the leasing 

 of the land around the observatory by Harvard College, and 

 that it is expected that the work will ultimately become a part 

 of that carried on directly by that University. 



Various schemes have from time to time been suggested for 

 utilising the power of the tides and waves as a motive force, 

 and ingenious models have been constructed showing the various 

 methods proposed. The plans consist generally either of a 

 system of reservoirs for storing the water at high tide and using 

 it by means of water-wheels or turbines as the tide falls, or else 

 by compressing air in a chamber and making use of its expan- 



