NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 213 



nence curve shoves maxima in the years 1884 and 1887-88, which 

 agree with the corresponding" maxima in the air pressure curve in 

 Bombay, the two prominence curves show a maximum in the year 

 1892 that falls with the minimum of the air pressure in Bombay. 



The Sicilian prominence curve shows also a secondary maximum 

 in the year 1897 that agrees with the minimum in the air pressure 

 in Bombay. On the other hand it shows the maximum of promi- 

 nences in the years 1904 and 1905 that falls with the maximum of 

 air pressure in Bombay. It is true that the two curves for promi- 

 nences do not fully agree. This is partially due to individual pecu- 

 liarities in the observations. At all events there are long periods of 

 time when the prominence curves have very slight variations, while 

 there are great variations in the corresponding meteorological varia- 

 tions on the earth. 



For the sun spots, as we know, the earlier investigations showed 

 no well-marked periods of several months or of a few years such 

 as the prominences indicate. However, as we shall show later, more 

 careful analysis brings to light such periods. It is possible that 

 the solar faculae or the calcium flocculi would give a better expres- 

 sion of these shorter periods in the variations of solar activity, but 

 we have not had opportunity to investigate this carefully. On the 

 other hand, it is a well known fact that the variations in the magnetic 

 forces on the earth have a very close relation to the variations in the 



appears from this that a considerable difference exists between the observa- 

 tions at the different observatories, such that, for example, the observations in 

 Rome on the whole show a considerably greater number of prominences per 

 day than the observations of Palermo and Catania, and they give also more 

 marked variations in the periods of few years as may be seen in the curves, 

 for example, figure 68, curve R. 



The values for the observed number of prominences per observational day 

 we have plotted in consecutive twelve-month means in the common way and 

 the values so found we have given in our curves ; for example, figure 68, where 

 the curve R represents the number of prominences for the observations of the 

 Roman Observatory, curve P for the observations in Palermo, and the curve C 

 for the observations in Catania. In figures 71, 74 and 75 we have repeated 

 these curves, R for the observations in Rome, P-C for the observations in 

 Palermo and Catania combined, and curve C for the observations in Catania 

 exclusively. 



Bigelow in 1908 has also given a list of prominences for each month for 

 the years 1872 to 1905, but this curve we could not use since the numbers 

 of prominences it showed were those of the whole months without reference 

 to the number of observational days, so that the months with few days had 

 few prominences even though the number of prominences at a time was large. 



