February i, 1900] 



NA TURE 



327 



methods of teaching, or covering ground not satisfactorily treated 

 in text-books, and reviews of books of the first importance, or 

 L,'roups of text-books on kindred subjects, giving an elementary 

 |)resentation of the history and treatment of the subject. Vol. 

 ii., which commences with the present year, will contain a 

 ^(.ries of articles by Prof. C. A. Scott, on von Standt's 

 I'leonutrie der Lage. 



Prof. A. E. VVric.ht describes in the Lancet the statistical 

 results of the anti-typhoid inoculations made by him among 

 British troops at a series of military stations in India. It ap- 

 pears that altogether 11,295 men were under observation, of 

 whom 2835 had been inoculated and 8460 had not. The per- 

 centage of cases of typhoid fever amongst the uninoculated was 

 '•5, and amongst the inoculated 0"95, a difference sufficiently 

 ^leat to warrant further extensive trials taking place. With 

 regard to the mortality the results are not so marked. Amongst 

 the uninoculated the percentage of deaths was 034, and 

 amongst the inoculated 0'2. A certain measure of protection 

 seems thus to have been conferred by the inoculation of the 

 quantities of dead typhoid culture, and when Prof. Wright's 

 remarks on the conditions under which the inoculations were 

 carried out are considered this conviction becomes intensified. 

 For instance, the inoculated men were, taken as a whole, men 

 who were much more liable to contract typhoid fever than the 

 uninoculated men, for the inoculated consisted to a large extent 

 of young men who had only recently arrived in India, while the 

 uninoculated consisted mainly of older and more seasoned — in 

 other words, of less susceptible — individuals. 



The relations of forest fires to insect ravages, insects to 

 forest fires, diseases of trees to insects, and insects to fungous 

 <liseases, are not obvious at first sight, but Dr. A. D. Hopkins 

 >hows in a report on the insect enemies of forests in the north- 

 west, just issued by the U.S. Department of Agriculture (Divi- 

 sion of Entomology), that there is a close connection, and, to 

 A Certain extent, inter-dependence, of all these factors in the 

 destruction of valuable forest products. Trees dying from injury 

 by fires, or weakened in vitality, offer favourable conditions for 

 the multiplication of vast numbers of destructive insects. More- 

 over, trees which have been killed by insects furnish, in their 

 fallen branches, standing and fallen partly decayed trunks, and 

 dry bark, a most favourable condition for the starting, rapid 

 spread, and perpetuation of forest fires. It is well known that 

 forest trees weakened by disease contribute to the multiplica- 

 tion of their insect enemies ; therefore the study of the insects 

 associated with unhealthy forest trees should lead to results of 

 economic importance. As an example of insects contributing to 

 the spread of fungous diseases. Dr. Hopkins reports that the 

 heartwood of the white fir throughout the region examined by 

 him was commonly rendered worthless by decay as the result of 

 wounds in the living bark made by Scolytus bark beetles. 



The Scientific American states that one of the most interest- 

 ing exhibits which will be sent from the United States to Paris 

 fi)r the forthcoming Exhibition will be a huge map of New 

 \oxV city, which is now in progress of construction under the 

 chief topographical engineer of the Board of Public Improve- 

 ments. It measures 28 feet by 24 feet, and is on a scale of 

 6x) feet to the inch, and includes all the boroughs of the great 

 city and a large part of the adjoining territory. The map 

 shows all the trees, parks, piers, ferries and railway lines, and 

 displays contour lines and elevations of every point in the 

 city; more than i.cxk) square miles of the territory are em- 

 Ijraced, and all buildings of any importance whatever are 

 indicated. 



Two novel swing-bridges over the river Weaver at North- 

 wich were described by Mr. J. A. Saner at the meeting of the 

 NO. 1579, VOL. 61] 



Institution of Civil Engineers, on January 23. Owing to the 

 nature of the foundations in the salt district, which, as is well 

 known, are seriously affected by the abstraction of brine and 

 salt from the subsoil, the design of the bridges presented 

 unusual difficulties. The average subsidence at the Northwich 

 bridge has been about 4^ inches per annum during the last 

 seventeen years, necessitating the raising of the girders to give 

 headway for the river traffic ; and it being impossible to raise 

 the streets in the immediate neighbourhood without partially 

 burying or raising the adjoining houses, the road gradients have 

 become as steep as i in 1 1. To obviate this inconvenience, and 

 to provide for the more efficient carrying on of the salt and 

 other trades on the Weaver, and also with the idea of eventually 

 passing coasting vessels with fixed masts, two exactly similar 

 swing-bridges have been built a little distance apart, in order 

 that one may be available in case of a breakdown. 



The superstructure of the two new bridges at Northwich, each 

 of which may be considered as weighing 300 tons, is supported 

 by a roller path and rollers, which in turn are carried upon a 

 set of piles, strongly braced together. Connected with, and 

 exactly under the centre of gravity of, the superstructure is a 

 circular pontoon or buoy, divided into two chambers. This 

 pontoon has the appearance of being suspended from the super- 

 structure, and in reality would be if the water were not present, 

 as it is entirely clear of both bottom and sides of the chamber 

 in which it is placed. Of this large buoy the lower chamber, 

 which has a displacement equal to 250 tons, is perfectly water- 

 tight and always submerged, so that its displacement is prac- 

 tically constant. The upper chamber is open at the top, and 

 either serves as an access to the lower chamber ; or, by varying 

 the amount of water allowed to enter it, increases or decreases 

 the buoyancy of the whole. It will be seen that the downward 

 pressure on the rollers and paths, due to the weight of the 

 superstructure, is partially counteracted by the upward tendency 

 of the pontoon, and is thus reduced, in the case under con- 

 sideration, to 300 - 250= 50 tons. By emptying the upper part 

 of the pontoon this may be further reduced within certain limits. 

 The difficulty presented by subsidence entailed careful con- 

 sideration as to the motive-power to be adopted for the bridge. 

 Pressure pipes of any kind being inadmissible, Mr. Saner 

 decided to adopt electrical power, and to use wire rope for 

 turning, as giving the most flexible connection between the 

 bridge and motor. The bridges are moved with remarkable 

 facility, and the consumption of current after they had been 

 working a short time, and all the bearings, &c., were free, only 

 amounted to ^ a Board of Trade unit for the complete cycle of 

 operations, viz. withdrawing wedges, opening and closing 

 the bridge, and replacing the wedges. 



We have received Part i., vol. xi., of the Indian Meteoro- 

 logical Miinoirs, containing the observations recorded during 

 the solar eclipse of January 22, 1898, at 154 stations, seven of 

 which were in close proximity to the central line of totality. 

 The observations were taken at intervals of five to fifteen min- 

 utes, and includes the barometer, thermometer, wind and cloud, 

 and occasionally other elements. These have all been reduced 

 and tabulated in the Calcutta Office according to Madras time, 

 and are, therefore, in this respect, strictly comparable. Beyond 

 this, no attempt is made to discuss the data. In looking over 

 the observations at the' stations of greatest obscuration one is 

 struck by the fact of the lull of the wind at the time of total 

 eclipse. For instance, at Seoni, where full obscuration lasted 

 from ih. 27m. to ih. 284m. p.m., the observer remarked, 

 " Everything quite quiet and calm, wind totally stopped from 

 ih. p.m. to 2h. lom. p.m."' The decrease of temperature 

 amounted to about 5" at several places. 



