. Report on the scientific results of the "Michael Sars" north Atlantic deep-sea expedition 1910, carried out under the auspices of the Norwegian government and the superintendence of Sir John Murray, , and Dr. Johan Hjort .. . ound by drawing straight lines fromthe rear point of the arrow to the different points markedalong the ellipse. The maximum of this resultant currentappears about 4 hours after the passage of the moon,with at velocity of 118 cm.,sec. towards N 60° E. These results are, however, uncertain because theobservations comprise 12 lunar hours only. The curvesin Fig. 42 sh
. Report on the scientific results of the "Michael Sars" north Atlantic deep-sea expedition 1910, carried out under the auspices of the Norwegian government and the superintendence of Sir John Murray, , and Dr. Johan Hjort .. . ound by drawing straight lines fromthe rear point of the arrow to the different points markedalong the ellipse. The maximum of this resultant currentappears about 4 hours after the passage of the moon,with at velocity of 118 cm.,sec. towards N 60° E. These results are, however, uncertain because theobservations comprise 12 lunar hours only. The curvesin Fig. 42 show considerable variations besides the semi-diurnal one. It is very probable that variations withshorter periods than 12 lunar hours exist, but there areevidently variations of a longer period too. When thesemi-diurnal variations are eliminated we obtain a resi-dual variation which manifests itself by a general increaseof the and decrease of the the period of observation. This variation maybe caused by a diurnal period in the tidal currents orby meteorological changes, or both. In any case it ATLANT. DEEP-SEA EXPED. 1910. VOL. ll PHYSICAL OCEANOGRAPHY AND METEOROLOGY 107 50. APRIL 3. Fig. 42. The and components of the current at Slat. 18, 9 metres. affects the results of the harmonic analysis with regardto the semi-diurnal variations and the rest current. The broken lines in Fig. 42 connect points (for 22and 10 ) which would have been found along thesame ordinates if the current had been composed of aconstant rest current and a semi-diurnal tidal current variations with a longer period than 12 lunar hoursare certainly not linear, but we may to some extent eli-minate them in our analysis of the semi-diurnal variationsby taking them as linear. We can then reduce the hourlyvalues which were used in the harmonic analysis doing so we obtain the following equations:t; = 21-6 — 380 cos 30 (H -^ 2) — 3-3 sin
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