case that the study of carbon compounds is being so vigorously prosecuted. . . . As to the value of the work, I believe that every fact honestly recorded is of value." No unprejudiced reader can but be struck with the improvement in quality which is manifest in the majority of the investigations now published. The great outcome of the labors of carbon chemists has been the establishment of the doctrine of the structure. That doctrine has received the most powerful support from the investigation of physical properties, and it may almost, without exaggeration, be said to have been rendered visible in Abney and Festing's infra-red spectrum photographs.
Limits of Stress on Iron Bridges.—Addressing the Mechanical Science Section of the British Association, Mr. B. Baker spoke of the want of understanding among engineers regarding the admissible intensity of stress on iron and steel bridges, concerning which "at the present time absolute chaos prevails. The variance in the strength of existing bridges is such as to be apparent to the educated eye without any calculation. . . . It is an open secret that nearly all the large railway companies are strengthening their bridges, and necessarily so, for I could cite cases where the working stress on the iron has exceeded by two hundred and fifty per cent that considered admissible by leading American and German builders in similar cases. . . . In the present day engineers of all countries are in accord as to the principles of estimating the magnitude of the stresses on the different members of a structure, but not so in proportioning the members to resist those stresses. The practical result is, that a bridge which would be passed by the English Board of Trade would require to be strengthened five per cent in some parts and fifty per cent in others before it would be accepted by the German Government, or by any of the leading railway companies in America." This undesirable state of affairs arises from the fact that "many engineers still persistently ignore the fact that a bar of iron may be broken in two ways—namely, by the single application of a heavy stress, or by the repeated application of a comparatively light stress. An athlete's muscles have often been likened to a bar of iron, but, if fatigue be in question, the simile is very wide of the truth. Intermittent action—the alternative pull and thrust of the rower, or of the laborer turning a winch—is what the muscle likes and the bar of iron abhors. From tests made several years ago by royal commissioners, the deduction was made that "iron bars scarcely bear the reiterated application of one third the breaking weight without injury, hence the prudence of always making beams capable of bearing six times the greatest weight that could be laid upon them." Hundreds of existing railway bridges which carry twenty trains a day with perfect safety would break down quickly under twenty trains an hour. Although many more experiments are required before universally acceptable rules can be laid down, "I have thoroughly convinced myself that, when stresses of varying intensity occur, tension and compression members should be treated on an entirely different basis."
Some Aspects of Heredity.—Mr. Francis Galton spoke, in the Anthropological Section of the British Association, from his researches in family histories and records, on types and their inheritance. He discussed the conditions of the stability and instability of types, and urged the existence of a simple and far-reaching law governing the hereditary transmission. From experiments he had made several years before on the produce of seeds of different size but the same species, it appeared that the offspring did not tend to resemble their parent-seed in size, but to be always more mediocre than they—to be smaller than the parents if the parents were large, to be larger than the parents if the parents were very small. The special subject of this paper was hereditary stature, where a similar law seemed to prevail. His data consisted of the heights of nine hundred and thirty adult children and their parentages, two hundred and five in number. The child inherits partly from his parents, partly from his ancestry. Speaking generally, the further his genealogy goes back, the more numerous and varied will his ancestry become, until they cease to differ from any equally numerous sample taken at hap-hazard from the race at large. Their mean stature will then be the same as that of
