206 THE POPULAR SCIENCE MONTHLY. 



the several seasons and the growth made during the same, I selected 

 from my meteorological records the maximum, minimum, and mean 

 temperature, and the rain-fall, of the six growing months of sjiring 

 and summer of each of the twelve years of growth. These extracts I 

 have tabulated, and have also appended to each season the thickness 

 of the ring formed, as measured on the oblique cut previously described. 

 An examination of this table shows a general relation of cause and 

 effect between high temperature and large rain-fall, and greater growth. 

 But it falls very far short of proving a general law of " so much heat 

 and so much water during the growing season, to produce so much 

 wood." For example, compare the years 1875 and 1878. The tem- 

 perature of 1878 for the season is better than 4 in excess of the sea- 

 son of 1875, and the rain-fall only a little over four inches less ; and 

 yet the growth of 1875 is seven times what it was in 1878. This 

 almost unparalleled growth of 1875 that is, as compared with the 

 other years can not be explained by the above general law. But I 

 think the May and June record of that year throws light upon it. 

 We see there a maximum heat in May of 96 (higher than I have ever 

 known it in an observation and record of twenty-five years), and a 

 mean temperature of the whole month, also unequaled, of 71; and 

 this great heat continued through the month of June, and no cold 

 spells after the heat set in sufficient to check the growth. Then, in 

 connection with this heat, the ground was well saturated with water 

 when this heated term began (May 6th) by 162 inch of rain on the 

 4th. From this on, to the 26th of June, 15 inches more of rain fell, 

 so apportioned over the time as to keep the ground saturated. This 

 synchronous excess of heat and water evidently produced the abnormal 

 growth. And probably, as this matter is further studied, it will be 

 found that these agents, rightly proportioned, operating synchronous- 

 ly, produce these thicker rings ; while as one or the other is in excess, 

 or absent, the growth is checked, and thus has time to condense and 

 harden, and form these sub-rings ; and the more frequent these alter- 

 nations, the greater the number of them. 



SCIENCE m EELATION TO THE AETS. 



By C. WILLIAM SIEMENS, F. E. S. 



II. 



AS is an institution of the utmost value to the artisan ; it requires 

 hardly any attention, is supplied upon regulated terms, and gives 

 with what should be a cheerful light a genial warmth, which often 

 saves the lighting of a fire. The time is, moreover, not far distant, I 

 venture to think, when both rich and poor will largely resort to gas as 



G 



