Mr. Crum on the Influence of the Moon. 248 



The following paper was then road. 



LIII. — On the supposed Influence of the Moon upon the Weather. 

 By Walter Crum, F.R.S., Vice President. 



There is no more common belief, even among those who make 

 accurate observations on other subjects, than that changes of the 

 weather are more decided, and occur more frequently at changes of 

 the moon than at any other period of the month. A similar influence 

 is very generally ascribed to the full moon ; and not a few look for 

 changes at the commencement of every quarter. 



I had abundant opportunity of observing the firmness with which this 

 opinion is held by a class of men who are placed in circumstances 

 that may be thought the most favourable for testing its correctness. 

 In December, 1820, I sailed in a Maltese vessel from Valletta to 

 Marseilles, and took six weeks to perform what is usually done in 

 ten days. I soon became desirous to gather opinions of the weather, 

 and found them to be formed entirely on the phases of the moon. 

 Every new quarter was to bring a favourable wind, and although we 

 were repeatedly disappointed, the next quarter was still anxiously 

 looked forward to for relief. During that voyage, my faith in the 

 moon, if I ever had any, was thoroughly shaken, and I afterwards 

 became desirous to procure facts which would enable me to form an 

 accurate opinion on the subject. I was not a little pleased, there- 

 fore, to meet, in the following year, with a paper by Professor Olbers, 

 of Bremen, " On the Influence of the Moon upon the Seasons ;" con- 

 firming most satisfactorily the views I had formed upon slighter 

 examination. 



As on all subjects where uncertainty prevails, and where men are 

 guided more by imagination than by fact, there is here the greatest 

 variety of opinion. In some of our almanacks minute directions have 

 long been given for predicting the weather for the succeeding half 

 month, from the hour of the day or night at which the moon enters 

 the first or the third quarter ; and I know that they obtain very general 

 credit, their antiquity forming an important argument in their favour. 

 For instance, if we have new or full moon at midday, we may expect 

 much rain in summer, and rain and snow in winter. If at midnight, 

 the weather will be fair in summer, and fair and frosty in winter; and 

 so on, for every two hours in the twenty- four. These predictions, or 

 rather rules for predicting, we are assured, have stood the test of half 

 a century ; but if, as is said, they were drawn up by Dr. Samuel 

 Clarke, from his own experience, they must have existed at least a 

 hundred and twenty years. 



I trust that the great prevalence of such impressions will excuse me 

 with the Society for calling their attention to it ; and if, to some of 

 its members, the statements I have collected are already familiar, they 



