296 



NATURE 



\July27, 1882 



b. Times of Observation 



2. Tbe hourly magnetical and meteorological observation 5 

 may be made according to any time, only the magnetica' 

 observations on the term days must always be made according to 

 Gottirgen time (mean civil time). The term days are always 

 the 1st and 15th of every month, except January, where tbe 2nd 

 is to be taken as the term day instead of the 1st. 



e. Order of the Observations 



3. The expeditions are free to choose the order of their 



itions as they think fit. 



d. Mtteorological Observations 



4. Air. Temperature. The mercurial thermometers should 

 be read to o°'l C, the spirit thermometers to at least o°'5 C. 



5. The thermometers should be verified at the Central Meteo- 

 rological Offices, and the spii it thermometers besides are to be 

 compared with a mercurial thermometer at the place of observa- 

 tion at as low temperature as possible. The zero point of all 

 thermometers used in the observations is to be determined afresh 

 from time to time. 



6. '1 he thermometers are to be placed at a height of at least 

 \\ to 2 metres above the ground, in a screen like that given by 

 Wild, and which will secure that without excessive interference 

 with the free circulation of the air about them they will be shel- 

 tered from all disturbing influences of radiation. 



7. The minimum thermometer for the determination of air 

 temperature must be placed under the same conditions as the 

 other thermometers. 



S. The temperature of the sea on the surface and at the depth 

 of every 10 metres is to be observed wherever possible. The 

 following are suggested as useful instruments for this purpose : — 

 sluggish thermometers by Eckmann, Negretti and Zambra, 

 Miller-Casella, &c. 



9. Pressure. Every station must at least have a standard 

 mercurial barometer and a good observing mercurial-barometer, 

 besides reserve barometers and aneroids. 



10. The barometers mu-t be verified by a Central Meteoro- 

 logical Office, and the observing barometer must be compared at 

 least every week once « ith standard barometer. 



11. Humidity. The psychrometer and the hair hygrometer 

 are to be used, but at low temperatures they must be compared 

 as often as possible with instruments for direct observation. 



12. Wind. The vane and Robinson's anemometer should be 

 arranged to be read off inside the observatoiy [vide the arrange- 

 ment of the Swedish instruments at Spitzbergen). The direction 

 of the wind is to be given for every 16 points and according to 

 true bearings. Its velocity should always be given according to 

 Robinson's anemometer, and also estimated Beaufort's scale. As 

 a reserve instrument for measuring the wind force, in case of 

 injury to Robinson's anemometer, Hagemann's anemometer 

 recommended itself as being simple in management and very 

 strong. 



13. Clouds. Form, amount, and direction of motion at 

 various heights, are to be observed to 16 points. 



14. Rainfall, &c. Occurrence and duration of rain, snow 

 Graupel (soft hail) are to be noted, and when possible the 

 amount. 



15. Weather. Thunderstorms, hail, fog, hoar-frost, and 

 optical phenomena are also to be noted. 



e. Observations of Terrestrial Magnetism 



16. In determination of absolute declination and inclination 

 the accuracy of one minute is to be aimed at, and in those of the 

 absolute horizonial intensity accuracy of 0,001 of its value. 



17. It is decidedly necessary, besides the absolute observations 

 in the observatory itself, to make a series of measurements in its 

 neighbourhood, in order to prove the existence of possible local 

 influences. 



18. The absolute observations must be conducted in the 

 closest connection and synchronou-ly with the readings of the 

 variation instruments, so as to render it possible to reduce the 

 indications of the lal er to absolute value of determination, e.g. 

 tbe absolute zero points of the different scales. The determina- 

 tions must be made so frequently that any changes which may 

 occur in the absolute value of the zero point of the scale of the 

 variation apparatus may be detected with the requisite accuracy. 



19. The observation of the variations should be extended to 

 all three elements of terrestrial magnetism, and it is desirable 

 that every station should have a complete duplicate system of 

 variation instruments so as to make comparative observations 



from time to time, and to avoid the risk of the interruption of 

 the observations by any accident. 



20. The variation instruments should have small needles and 

 the variation of horizontal intensity should be observed at least 

 on one system with theunifilar apparatus with reflectors. Owing 

 to the serious disturbances which may be expected, the scales of 

 the variation instruments should be extended to at least 5° on 

 each side, and as in certain cases deviations may even exceed 

 thes: limits, the observers must be prepared to be able to 

 measure even such greater excursions. The apparatus should be 

 erected so as to facilitate as far as possible simultaneity of the 

 observations. 



21. During the whole time the variations should be read 

 hourly. It is desirable that two readings shi uld be made with 

 an interval of a few minutes, for instance, before and after the 

 exact hour. 



22. As term days the first and fifteenth day of each month are 

 fixed (only January 2 instead of I is taken) ; the days are from 

 midnight to midnight, Gottingen time (mean civil time). The 

 readings are to be made every five minutes, and always at the 

 exact minute, and the three elements should be read as quickly 

 as possible one after the other in the following order : — 



Horizontal Intensity — Declination — Vertical Intensity. 



23. On such term days during a whole hour, observations every 

 twenty seconds are to be made, but only of the declination. 

 These increased observations for one hour for the different term 

 days are given in the following table : — 



Gottingen Civd Time, 



f. Auroral Observations 



24. The auroras to be observed hourly with regard to shape, 

 colour, and motion ; the position to be given according to true 

 bearings. Tbe brilliancy of the different parts is to be estimated 

 according to the scale o — 4 (vide Weyprecht : " Instructions for 

 the Observation of Aurora, 1S81 "). In general, illumination 

 of the aurora is sufficient to read printed mat er ; its brilliancy 

 is to be estimated in this way and by the method employed in 

 testing eyesight (as, for instance, according to the scale of Jaeger 

 in 'Vienna). 



25. On the term-days, continuous auroral observations will 

 be carried out. 



26. Especially remarkable in-tances of auroras and magnetic 

 disturbances must be made the subject of special investigations, 

 in order to render it possible to determine the connection of the 

 variations of the phases of these two phenomena. 



g. Astronomical Observations 



27. As as much simultaneity as possible is a main object of the 

 observations, determinations of position and time are to be 

 carried out by instruments erected solidly (universal instrument, 

 transit instrument, &c), but these are not to exclude the use of 

 good reflecting instruments. Every effort should be made as 

 as quickly as possible to determine the longitude of the place 

 with sufficient accuracy for the objects of expedition. 



