54 



stemme de her beskrevne Resultater kun maadeligt overens. 

 Ifølge den af Wackerbarth efter Ekmans Observationer 

 beregnede Formel er Temperaturen for Tæthedsmaximum 

 hos Søvand af Egenvægt 1.02707 = — 4.°04, medens Lig- 



ningen = med de af mie fundne Ooefncienter giver 



ilt 



Temperaturen — 4. 45. 



Paa Grand af denne gjennemførte < >verensstemmelse 

 mellem Ekmans og mine Resultater, har jeg ikke fundet 

 det fornødent at bestemme Udvidelsen af Vandprøver af 

 lavere Egenvægt. men har uden videre anvendt Ekmans 

 Observationer paa de faa Puncter. hvor jeg til Reduction 

 af de paa den norske Nordhavsexpedition aflæste Egenvæg- 

 ter har havt Brug for dem. Ved Hjælp af de ovenfor op- 

 førte Værdier for Sovandets Yolumina ved forskjellige 

 Temperaturer kan man nu beregne de (Jorrectioner. hvor- 

 med ile ved vilkaarlige Temperaturer aflæste Egenvægter 



17. °5 

 maa forbedres foråt reduceres til ^-^ ■ Correctionerne . 



17.°o 



hvori ogsaa indgaar et Led. der afhænger af Aræometrenes 



Udvidelsescoefficient, 1 tindes sammenstillede i nedenstaaende 



Tabel. 



Hvor den Temperatur, hvorved Aflæsningen tforetages, 

 ikke fjerner sig meget fra Normaltemperaturen 17. "5. kau 

 disse Correctioner, der strengt tåget kun gjælde for Søvand 

 af Egenvægt omkring 1.027. ogsaa uden mærkelig Feil an- 

 vendes for Vandprøver af en derfra temmelig forskjellig 

 Egenvægt. Hvor derimod den Temperatur, hvorved Arlæs- 

 ningen foretages. ligger langt fra 17.° 5, ere disse Correc- 

 tioner kun gyldige for et meget begrændset Iuterval. 



Efteiat saaledes de aflæste Egenvægter ved Anbrin- 

 gelse al' disse Correctioner ere reducerede til Normaltem- 

 peraturen. staar det endnu tilbage at befrie dem for de ved 

 de benyttede Aræometre heftende constante Feil. 



Til Aåæsning af saa godt som alle paa Expeditionen 

 bestemte Egenvægter benyttedes kun .'i Aræometre, to paa 

 første Togt og et paa de to sidste. Af de to først nævnte, 

 der af Svendsen før ('dreisen vare udvalgte af de øvrige, 

 fordi de bavde vist sig at stemme særdeles vel overens, er 

 desværre det ene senere bleven knust, det andet er endnu 

 i Behold og er sammen med det paa sidste Togt benyttede 

 bleven corrigeret af mig. 



S saadan benyttedes 0.000020. 



A. Wackerbarth from Ekmans observations, the tempera- 

 ture for the maximuni density of sea-water with a specific 



gravity of 1.02707 is — 4. "04. whereas the equation — 



gives, with my coefficients. a temperature of — 4. "45. 



Relying. then. on the close agreement between 



Ekman's results and my own. I have not determined 



the expansion in samples of sea-water with a lower 



specific gravity. hut have adopted Ekman's observations, 



for reducing. when needful, the specific gravities read on 



the Norwegian North-Atlantic Expedition. By means of 



the values, tabulated above. for the volume of sea-water at 



different temperatures. the corrections which serve to reduce 



17. "5 

 specific gravities read at any given temperature to ' _ 



may be computed. These corrections. into which the coef- 

 ficient of expansion of the areometer 1 enters as a factor, 

 are given in the following Table. 



When the temperature is not far removed from the 

 normal temperature. 17. "5. these corrections. which. strictly 

 speaking. apply only to sea-water with a specific gravity 

 of about 1.027. may. without involving any appreciable 

 error in the result, be likewise adopted for samples of 

 water whose specific gravity differs considerably from that 

 expressed by the above formula ; but when. on the other 

 hand. the temperature at which the specific gravity is read 

 and that of 17." Ti lie far apart, the iuterval for which these 

 corrections will serve is but very limited. 



After reducing by means of these corrections the 

 specific gravities to the normal temperature. there still 

 remains to eliminate the constant error of the areometer. 



For reading almost all of the specific gravities determ- 

 ined on the Expedition, only 3 a.reometers were made use 

 of. two on the first cruise and one on the two last. Of 

 the two former, which. having been found to agree uncom- 

 monly well, Mr. Svendsen lind selected previous to his 

 departure, one was unfortunatehj afterwards broken; the 

 other is still in pcrfect order, and was. together with that 

 made use of on the last voyage, corrected by myself. 



1 Thai adopted was 0.000026. 



