32 SCIENCE. [Vol. VII., No. 153 



They should be maps in which the various features 

 of surface are clearly, carefully, and fully drawn. 

 I do not mean maps full of names, but full of fea- 

 tures. To illustrate : Where are the Alps? The Alps 

 are in Switzerland ; and the schoolboy finds on his 

 map ' Alps ' printed on the south side of that portion 

 labelled ' Switzerland.' A good map would show at 

 least four ranges there ; and proper maps of Austria, 

 Italy, and France, would teach him that ' Alps' is a 

 generic term with at least thirteen applications in 

 southern Europe. 



Norway and Sweden appear on most school-maps 

 with but one or two rivers, because, I suppose, there 

 is no long and large stream there important enough 

 to have its name memorized ; but what an idea does 

 such a map give of that country ? I can count over 

 sixty rivers there on a map in Andree ; and enough 

 of them should be drawn, even if without naming, to 

 show the true character of the surface. 



Similar instances could be given by the dozen. But 

 I want to take up another point. When are we to 

 see a geography with an index ? Studying geography 

 by the topical method, an index is well-nigh indis- 

 pensable. By any method, twice as effective work 

 can be done if the material can be viewed from the 

 stand-point of the kind of feature, production, occu- 

 pation, or race, as well as in relation to this or that 

 political subdivision. 



I do not think it too much to insist on, that every 

 ocean, sea, gulf, bay, strait, channel, lake, sound, 

 harbor, canal, river, waterfall, bight, firth, bayou, 

 roadstead, etc. ; every land feature, every product, 

 occupation, language, religion, form of government, 

 town and political division, — in short, every thing 

 namable that has been mentioned in the text or ap- 

 peared by name in the maps, — should be indexed by 

 page or section, and. in case of map features, with 

 latitude and longitude. 



Why, even in Morden's ' Geography rectified,' pub- 

 lished in 1693, there is a copious index, not to men- 

 tion later works (1809, 1831) likewise favored. 



With an index to aid him, a scholar can classify, 

 compare, and infer ; and the value of the text-book 

 would be doubled. 



Nor would it be difficult to mention other ways in 

 which our geographies could be improved. But if we 

 can first have some better maps and an index worthy 

 the name, we shall have gained much. I hope you 

 will not be content with a few leaders. The matter 

 is one of no slight importance. Perhaps, if our pub- 

 lishers read Prince Kropotkin's article in the Decem- 

 ber number of the Nineteenth century, they would be 

 inspired to do better. Let us hope they will. 



C. H. Leete. 



New York, Dec. 31. 



The temperature of the moon. 



Mr. Langley does not seem to have examined my 

 condition for determining the moon's temperature 

 with sufficient care. It is true that in the equation 

 B moon of maximum radiating power was assumed ; 

 but it had been first shown that the temperature of 

 such a moon must be the same as that of any other, 

 provided the relative radiating and absorbing powers 

 are the same, as is usually assumed. The equation 

 is between the absolute rate of radiation and absorp- 

 tion of heat, in which r, the relative radiating 

 power, entern as a factor on the one side, and a, the 

 relative absorbing power, on the other. If these are 

 equal, of course they can be omitted, which is the 



same as using unity as the relative radiating and 

 absorbing powers, and so the same as assuming that 

 the moon has a maximum relative radiating and 

 absorbing power. The relative radiating and absorb- 

 ing powers, and the proportion of heat reflected, do 

 not, therefore, come into the condition at all. It 

 cannot be said with propriety that the moon loses 

 heat by reflection, as stated by Mr. Langley ; for the 

 reflected heat has not been appropriated by absorp- 

 tion, and therefore cannot be said to be the moon's 

 heat. It has come to the moon's surface and been 

 rejected, and it has nothing to do with its tempera- 

 ture. The condition which determines the static 

 temperature is, that the rate with which heat is 

 radiated must be exactly equal to that with which it 

 is absorbed. When this is the case, there can be 

 neither increase nor decrease of temperature. 



But perhaps this matter will be more readily com- 

 prehended by looking at it in a less mathematical 

 way. We have a mocn, say. with a surface of maxi- 

 mum relative radiating and absorbing power, and 

 with a temperature below the static temperature 

 corresponding to the rate with which it is receiving 

 heat. With this temperature, the absolute rate 

 with which the moon radiates heat is less than that 

 with which it is receiving and absorbing it, and the 

 difference goes toward raising the temperature of 

 the body. But as the temperature increases, and 

 with it the rate of radiating heat, though not pro- 

 portionally, it after a time rises to that temperature 

 at which the rate with which heat is radiated from 

 the moon is exactly equal to that with which it is 

 received and absorbed by it, and its temperature 

 then remains stationary. This, expressed in a math- 

 ematical form, is the equation of condition. 



But now suppose that the moon's surface is such 

 that it radiates and absorbs heat at only half, or any 

 other proportion, of the rate that one of maximum 

 relative radiating and absorbing power does. Our 

 condition is still satisfied ; for although the moon's 

 surface now is radiating heat at a rate which is only 

 half, or any other assumed proportion, of what it 

 was before, it is also absorbing at only the same rate, 

 whatever it may be, and there is no change of tem- 

 perature needed to satisfy the condition of static 

 temperature. Hence, so far as the static tempera- 

 ture of the moon is concerned, it is no matter what 

 part of the heat received is absorbed, and what 

 reflected ; these being complementary to each other, 

 and both together equal to the heat radiated by a 

 moon of maximum relative radiating power, under 

 the condition of a static temperature. Of course, 

 our condition for determining the temperature is not 

 applicable where there is a rapid increase or decrease 

 of temperature. Wm. Ferrel. 



Washington, Jan. 4. 



Yankee. 



In a paper upon the origin of 'Yankee Doodle,' 

 read lately before the New York historical society, 

 Mr. George H. Moore states that the word ' Yankee ' 

 is pure Dutch. ' Yankin,' he says, in the vocabulary 

 of the early New York Dutch, meant 'to grumble, 

 snarl, or yelp,' and its derivative noun meant 'a 

 howling cur.' 



But where did the New York Dutch get the word ! 

 I think from the Indians. Peter Martyr says that 

 Sebastian Cabot named the coasts of Newfoundland 

 and thereabouts the land of baccalaos, because in 

 the seas he found a multitude of large fish which 



