352 THE POPULAR SCIENCE MONTHLY. 



that is wanted, which is dependent upon a very well-defined minimum 

 thickness of the coating. In this is involved a question of interference- 

 colors, the same as is involved in soap-bubbles and the temper-colors 

 of steel, in which there must be an exact difference in the wave-lengths 

 of the light reflected from the upper and lower surfaces of the coat- 

 ing. Many colors, like steel-green, require repeated trials to be brought 

 out in their full beauty. The advance that has been made in this art 

 has been illustrated to me in a specimen-sheet of beads which are de- 

 signed to make trimmings exactly corresponding in color for silks of a 

 very great variety of shades. 



In addition to the glass industry, a very extensive interest has been 

 developed in the manufacture of brass, bronze, pinchbeck, etc., in 

 which use is made of various galvanic coatings of metal. These 

 branches of the art are carefully taught in the industrial school at 

 Gablonz. Translated for the Popular Science Monthly from Uhsere 

 Zeit. 



-+*+- 



GEOLOGICAL CLIMATE IN HIGH LATITUDES.* 



By C. B. WAERLNG, Ph. D. 



THE peculiar climate of geological times has hitherto been treated 

 as if it were a question of temperature only. Scientists have 

 sought the cause of the remarkable warmth in arctic regions, but have 

 left untouched other questions of equal and perhaps greater impor- 

 tance. 



One can hardly contemplate the climatic conditions of that remote 

 period without inquiring how there could be other than a great differ- 

 ence of temperature between the summers and winters of lands less 

 than 8 from the pole ; and how could circumstances environments 

 so unlike as the four or five months of day of those regions, and 

 the twelve-hour day of the tropics, fail to induce great specific dif- 

 ferences in their fauna and flora. The questions spontaneously arise : 

 Is it possible that the days and nights in high latitudes were then as 

 they are now ? Must not the climate have been warm in January 

 as well as in July ? Must not the influences of the solar rays the 

 actinic force have been distributed through the year with at least 

 approximate uniformity in high as well as low latitudes ? It is these 

 questions, as well as those of temperature, that I shall consider in this 

 paper. I propose to study the record left by the plants and animals 

 which lived in those remote days. Some of their more obvious teach- 

 ings are startling enough. Regions where now vegetation is of the 

 scantiest character, where no trees exist save a few dwarf willows, 

 where the winters are cold almost beyond endurance, were, as late as 



* Read before the New York Academy of Science. 



