Oct. 1 8, 1883] 



NA TURE 



605 



adopted at the Cavendish Laboratory for comparing resistance 

 coils sent to be tested with the B.A. units. 



Report of the Committee on the Harmonic Analysis of the Tides 

 was read by Prof. Adams, who said that the Indian Govern- 

 ment were entitled to great gratitude for carrying on tidal obser- 

 vations for many years on a thoroughly scientific system, and he 

 thought they might be held up as an example to our own Govern- 

 ment, which was very niggardly in these matters. He suggested 

 that tidal observations should be made on the coast of the 

 English Channel, as there were certain peculiarities in the tide 

 which ought to be investigated. 



Report of the Committee at/pointed to Cooperate with the 

 Scottish Meteorological Society in making Meteorological Ob- 

 servations on Ben Nevis was drawn up by Mr. Murray for 

 Prof. Crum Brown. Stations had been established at various 

 points at which observations were made by the observer, 

 Sir. Wragge, half-hourly as he ascended or descended the 

 mountain. Simultaneous observations were made at Fort 

 William. The diurnal curves for pressure, temperature, and 

 humidity have been drawn, and show the insular character 

 of the climate markedly. At the top the degree of saturation 

 and its persistency is important. In 1SS1 this was a specially 

 marked feature under the approach of numerous cyclones from 

 the Atlantic; in 1882 anti-cyclones prevailed, and there were 

 frequent changes from saturation to extreme dryness — a dryness 

 comparable with that of the Sahara — occurring in very short in- 

 tervals uf time. This extreme dryness was accompanied by a 

 very high teoiperature. The results are to be analysed shortly 

 by Mr. Buchan for the Scottish Meteorological Society. 



Sixteenth Report of the Committee appointed for the Purpose 

 of Investigating the Rate of Increase jf Underground Temperature 

 Downwards in various Localities of Dry Laud and under Water 

 was read by Mr. J. Glaisher. The observations were made at an 

 artesian well at Southampton, Dolcoath Mine, North Seaton 

 Colliery, Ashton Moss Colliery, and Ashton-under-Lyne. The 

 report concluded by stating that if we assumed 1° in 57*8 feet as 

 the rate for the St. GotFird Tunnel, and also for the Mont 

 Cenis Tunnel, the effect upon the general mean for all places 

 will be t) make it I s F. in 60 feet, instead of I" F. in 64 feet. 



SKCTION A — Mathematical and Physical Scienxe 



On the Forms of the Sun's Influence on the Magnetism of the 

 Earth, by Prof. Balfour Stewart. — The author endeavoured to 

 show that there are two forms of solar influence : — 



A. That which produces the diurnal variation, the range of 

 which is greatest a little after the time of maximum sunspot 

 frequency. 



B. That which produces a magnetic change on the earth as a 

 whole ; and this, too, acts in such a manner that the intensity of 

 terrestrial magnetism is apparently greatest after a maximum of 

 sunspots. 



It is with this second form of influence that the author deals, 

 and he endeavours to show that it leads — 



1. To simulianeous increments or decrements of the horizontal 

 force at various states as observed by Broun. 



2. To two maxima of horizontal force at the solstices and two 

 minima at the equinoxes, as observed also by Broun. 



3. It appears that the strength of solar action, when the sun is 

 favourably disposed with regard to the northern hemisphere 

 (June) is greater than when it is favourably disposed with regard 

 to the southern hemisphere (December), a circumstance which 

 leads to an annual variation. 



4. It also appears that it is what has been termed the induc- 

 tion system of the earth that is thus affected by the sun. 



On the Heating Power of the Sun's Rays at Loudon and at 

 Kew, by Professors Roscoe and Balfour Stewart. — The observa- 

 tions di-cussed were made by Campbell's method, in which a 

 spherical glass lens had its focus along the surface of a hemi- 

 sphere of wood, so that, whenever the sun shone, a portion of 

 the wood was burned. The wooden hemisphere was renewed 

 twice every year, namely, at the solstices. The following results 

 were obtained from the observations, by a process in which the 

 burned volume was filled up and the increase in weight accu- 

 rately measured : — 



l. The heat of the sun for the half year between the June and 

 the December solstice is greater than that for the half year 

 between the December and the June solstice, but this difference 



is more marked at London (Board of Works) than at the Kew 

 Observatory. 



2. The annual value of the sun's heat is greater at Kew than 

 at London in the proportion of 100 to 5S. 



3. The annual value of the sun's heat is peculiarly great about 

 the period of maximum sunspots, but there are indications of a 

 double heat-curve for one of sunspots, so that there is a sub- 

 sidiary maximum of heat about the period of minimum sunspots. 



On Suppostd Sunspot Inequalities of Short Period, by Prof. 

 Balfour Stewart and William Lant Carpenter, M.A. — Putting 

 aside in the meantime the question of true or nearly apparent 

 periodicity, the authors exhibited certain results obtained by this 

 application of a method for detecting unknown inequalities in a 

 mass of observations. This has been applied to thirty-six years.' 

 ob-ervations of sunspots, which have been divided into three 

 series of twelve years each. Two apparent sunspot inequalities 

 of about twenty-six days come out very prominently by this 

 treatment, appearing for each of the twelve years in the same 

 phase, and to very nearly the same extent. If the average value 

 of sunspots for each year be reckoned = 1000, this is reduced to 

 less than 900 at the minimum of the inequalities, and increased 

 to more than 1 100 at their maximum, so that the average range is 

 more than one-fifth of the average value, a result of very con- 

 siderable prominence. 



Prof. Chandler Roberts read a paper On the Rapid Diffusion 

 rf Molten Metals. The two metals chosen weie lead and gold 

 inclosed in a letter U-shaped tube, the lead occupying the lower 

 portion of the tube, and the gold being put in at the top of one 

 limb. After about forty minutes Prof. Roberts found that the 

 tw o metals had been thoroughly mixed. — Sir W. Thomson called 

 attention to the extreme importance of this with reference to 

 metallic alloys, and remarked that it resembled the aiffusion of 

 gases or of heat in a gas rather than of a solid in a liquid. Salt 

 would take years to diffuse in a similar manner through water. 



Mr. W. G. Black described a simple form of marine anemo- 

 meter, in which the pressure of the wind on a sail of known area 

 was registered by a spring balance. The sail could be easily 

 placed in any required position on the ship, and set by means of 

 a vane to the proper angle with the wind. — The arrangement 

 was criticised by Prof. Hele Shaw, who described a form of his 

 own which he had used for measuring water currents. This 

 consisted of two light vanes, movable about the same vertical 

 axis, and pressed outwards by a spring. The wind tended to 

 make the vanes close up together, and their motion gave an 

 indication of its velocity. 



Papers on The Standard of White Light, and on The 

 Relation between Temperature and Radiation, by Capt. Abney, 

 and Sir C. W. Siemens respectively. Capt. Abney suggests 

 as a high temperature standard an incandescent lamp. The 

 light of this is compared by means of the spectrophotometer 

 with that from Prof. Vernon Harcourt's standard lamp, after- 

 wards described. The green light in the neighbourhood of E 

 should be about one and a half times that of the gas standard, 

 while the red light should be the same in the two. In a recent 

 paper Capt. Abney criticised some of Sir W. Siemens' s experi- 

 ments of a similar nature. Sir William had used platinum wire 

 in air instead of carbon in a vacuum, and the paper read was a 

 reply. — In the discussion Dr. Schuster pointed out that a similar 

 method, free from many of the difficulties under consideration, 

 had been suggested by the late Prof. Clerk Maxwell, and 

 apparatus for making the experiments was constructed by him 

 shortly before his death. 



Prof. Vernon Harcourt gave a description of a lamp for pro- 

 ducing a standard light. It was arranged for burning- air and 

 the vapour of petroleum, mixed in the proportion of three cubic 

 inches of vapour at a temperature of Go F. to one cubic foot 

 of air. The mixed gas is allowed to escape from a hole of a 

 quarter of an inch in diameter, and burn in a flame two and a 

 half inches high. Prof. Harcourt showed that the height of the 

 flame was an index of the proportion in which the ga-es mixed, 

 and was constant when the mixture remained constant. 



Mr. E. P. Culverweli read a paper On the Probable Explana- 

 tion of the Effect of Oil in calming Waves in a Siorm. He 

 said w hen the surface of the sea had become smooth after a 

 storm it was very common for long rollers to break . in a sand- 

 bar. If there were no wind and the sea was glassy, these would 

 not break until quite close to the shore, even though ihe ordinary 

 theory pointed to their breaking earlier, unless there was a force 

 directed opposite to that of their motion. When exerted on the 

 waves, such a force might be supplied by the wind ; but if it 

 rose in any direction the waves broke much sooner. This result 



