31''^ THE CLIMATE OF LOUREiXQU iMAROUES. 



-\s is nalLiral, the number of hours of sunshine is verv 

 cio^'^ly connected with cloudiness. 



The Jordan Siuishine recorder is employed at the Observa- 

 tor}-, Ijut has the inconvenience of recording the observations 

 with an error of from i to 2 %, owing to the sheets not printing 

 when the sun is low. 



The percentage of hours of stmshine is in the universe ratio 

 to rain and cloudiness. This can be seen from Tal)le XIV and 

 the diagram recording the percentage of sunless hours, cloudi- 

 i'e>s and rain. 



This relation is not perfect, and it so happens that the months 

 ot lower percentage of sunshine, (Jctoljer and November, are not 

 those of greater rain and cloudiness. • 



If we add the percentage of the hours of sunshine and 

 cloudiness, we shall see that this addition varies between Ii8 and 

 Qy, respectively, in the months of greatest rainfall and in the 

 driest ones, because the percentage of cloudiness oscillates be- 

 tween wider limits — 62 and 24 — than the ])ercentage of sunshine 



X'arious formuke have been introduced to connect these two 

 elen:ents. but this is rather a difhcult matter, seeing that it is possi- 

 I'le to register a great quantity of clouds without hiding tht sun. 



The highest figure in minutes of sunshine is registered, as 

 seen from Table No. X\' ,from XIII to XVI, that is during the 

 hotirs of greater heat and wind velocity, and decreasing steadily 

 toward simrise and sunset. When it increases, a retardation is 

 noticeable from XI to XIII, and during the decrease the latter is 

 more pronounced from X\'l to XVII. (In Lourengo Marques the 

 sun is above the horizon all the year round u]) to 5'^ 8' p.m.) These 

 alterations are tmdotil)tedly connected with those of the other 

 elements alreadv mentioned. 



These facts are common to all the months, with a slight 

 dift'erence. In the months of higher percentage of hours of 

 simshine the increase takes place more often from X to XVI. 



During three years of observation there were 45 days of no 

 sunshine, days when no printing of the " sunshine " paper took 

 place, 15 days when it printed during less than 10 minutes, and 

 46 days from 10 minutes to i hour. 



ACTTNOMETER AND SoLAR AND NoCTURXAL RaDIATIOiV. 



I'he importance of the study of solar radiation is well known 

 owing to its influence in all Meteorological elements. 



At the Observatory a Marie-Daw actinometer is employed, 

 and the Bouger formula is used. This actinometer's records are 

 not, as everyone knows, reliable, for different reasons, principally 

 on account of the absorption of some calorific rays by the glass. 



Ex])eriments made, especially those of Professor Crova, 

 ^hfnv that the heat received from the sun attains its maximum 

 at an intermediate period between winter and summer, in May in 

 the northern hemisphere ; during summer the intensity diminishes 



