96 



THOUGHTS ON THE INFLUENCE OF ETnER 



The mean day of the interval separating these seasons of warmth, must be more ad- 

 vanced in the year than the 8th September. 



Have such seasons been observed ? 



Have names been assigned to them'? 



Since the earliest days of civilization, it has been known that the greatest heat of sum- 

 mer does not coincide with the summer solstice. The ancient Egyptians, noticing that 

 certain days, remarkable for sultry heat, occurred about the beginning of July, at which 

 time the dog star emerged from the sun's rays, gave the name of the star to the season, 

 which is generally known as the canicular, or dog days. According to the almanacs, 

 they are reckoned about forty, beginning on the 3d July, and ending the 11th August. 

 This was doubtless true in the days of the Pharaohs, but, at the present time, the canicular 

 days are correctly estimated by M. Bescherclle to begin about the 24th July, and end the 

 26th August. 



Mr. Brande says, " Owing to the precession of the equinoxes, the heliacal rising of Sirius 

 now takes place later in the year, and in a cooler season; so that the dog days have not 

 now that relation to the particular position of the dog star, from which they obtained 

 their name." 



In this I must disagree with Mr. Brande. The dog days still bear their old relation to 

 the rising of the dog star. 



Astronomers have not yet discovered that the sun's axis undergoes any change in posi- 

 tion, though theoretically it must from planetary influence, revolve about the pole of the 

 ecliptic, just as the earth's axis does, but in an inconceivably long period. We may, there- 

 fore, consider the sun's axis as firmly fixed as the place of Sirius, and look for a continu- 

 ance of the occurrence of the dog days with the heliacal rising of Sirius. 



Besides the heat and sultriness which characterize the dog days, there is another feature 

 which is a very usual attendant, viz., an obscurity in the atmosphere which does not appear 

 to be associated with moisture, smoke, or dust. It sometimes comes on so rapidly that, 

 in the course of four or five hours, a whole landscape, as far as the eye can see in every 

 direction, is affected by it. I have known this state of things to continue six days at a 

 time, in spite of the intervention of a strong wind and rain. 



It may possibly never be determined what the origin of this obscurity is. I will ob- 

 serve, however, that it is a part of this theory of ethereal currents that, during the dog 

 days, our planet is passing through the substance of the zodiacal light. 



The only explanation of the cause of the canicular days, I have ever heard of, is that of 

 the Egyptians ; viz., the malignant influence of the dog star. 



If M. Bescherclle be correct in his estimate of the number, and time of occurrence of 

 the dog days, viz., from the 24th July to the 26th August inclusive, their number is thirty- 

 four, and the morning of the 10th August is the period of their greatest intensity. 



