492 KANSAS CITY REVIEW OF SCIENCE. 



lected from my meteorological records the maximum, minimum, and mean tem- 

 perature, and the rain-fall, of the six growing months of spring 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 be- 

 tween high temperature and large rain-fall, and greater growth. But it falls very 

 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 temperature of 1878 for the season is better than 4° in ex- 

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

 yet the growth of 1875 is seven limes what it was in 1878. This almost unparal- 

 leled growth of 1875 — that is, as compared with the other years — cannot be ex- 

 plained 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 unequalled, of 71°; and this 

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

 set ii> sufficient to check the growth. Then, in connection with this heat the 

 ground is well saturated with water when this heated term began (May 6th) by 

 I "62 inch of rain on the 4th. From this on, to the 26th day June, 15 inches 

 more of rain fell, so apportioned over the time as to keep the ground saturat- 

 ed. 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 synchronously, 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 alternations, the greater the number of them. — Popular 

 Science Monthly, Dec. 1882. 



GEOLOGY. 



SUPPOSED JURA-TRIAS OF THE FRONT RANGE OF COLORADO. 



JOHN K. HALLOWELL, DENVER, COLO. 



I feel that the actual existence of the Jura-Trias in Colorado is so questiona- 

 ble, that after giving what authorities I have at hand, I desire to call attention to 

 a. fact or two ; and also record a recent discovery in the sandstones of the St. 

 Vrain, Colo., hoping it may lead to the further investigation, by those more able 



