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THE POPULAR SCIENCE MONTHLY. 



to convey our ideas to them, rather than to 

 devise any language, or code of signals, by 

 means of which they might communicate 

 theirs to us. No doubt, the former process 

 is interesting and instructive, but it does 

 not carry us very far. Under these circum- 

 stances, it has occurred to me whether some 

 such system as that followed by deaf-mutes, 

 and especially by Dr. Howe with Laura 

 Bridgman, might not prove very instructive, 

 if adapted to the case of dogs. Accordingly 

 I prepared some pieces of stout cardboard, 

 and printed on each in legible letters a 

 word, such as ' food,' ' bone,' ' out,' etc. I 

 then began training a black poodle, ' Van ' 

 by name, kindly given me by my friend 

 Mr. Nickalls. I commenced by giving the 

 dog food in a saucer, over which I laid the 

 card on which was the word ' food,' placing 

 also by the side an empty saucer, covered 

 by a plain card. * Yan ' soon learned to dis- 

 tinguish between the two, and the next stage 

 was to teach him to bring me the card ; this 

 he now does, and hands it to me quite pret- 

 tily, and I then give him a bone, or a little 

 food, or take him out, according to the card 

 brought. lie still brings sometimes a plain 

 card, in which case I point out his error, 

 and he then takes it back and changes it. 

 This, however, does not often happen. Yes- 

 terday morning, for instance, he brought 

 me the card with ' food ' on it nine times in 

 succession, selecting it from among other 

 plain cards, though I changed the relative 

 position every time. No one who sees him 

 can doubt that he understands the act of 

 bringing the card with the word ' food ' on 

 it, as a request for something to eat, and 

 that he distinguishes between it and a plain 

 card. I also believe that he distinguishes, 

 for instance, between the card with the word 

 ' food ' on it and the card with ' out ' on it. 

 This, then, seems to open up a method 

 which may be carried much further, for it is 

 obvious that the cards may be multiplied, 

 and the dog thus enabled to communicate 

 freely with us. I have as yet, I know, made 

 only a very small beginning, and hope to 

 carry the experiment much further, but my 

 object in troubling you with this letter is 

 twofold. In the first place, I trust that 

 some of your readers may be able and will- 

 ing to suggest extensions or improvements 

 of the idea. Secondly, my spare time is 



small, and liable to many interruptions ; 

 and animals also, we know, differ greatly 

 from one another. Now, many of your 

 readers have favorite dogs, and I would ex- 

 press a hope that some of them may be dis- 

 posed to study them in the manner indicated. 

 The observations, even though negative, 

 would be interesting ; but I confess I hope 

 that some positive results might follow, 

 which would enable us to obtain a more cor- 

 rect insight into the minds of animals than 

 we have yet acquired." 



Salts in Rivers and in the Sea. The 

 sea, it is well understood, is fed with salt 

 as well as with water, by the rivers. The 

 question then arises naturally, How is it that 

 the rivers admitting that they are mildly 

 salt, although they appear to be fresh dif- 

 fer from the ocean in the kind as well as in 

 the strength of their saltness ? Mr. W. Mat- 

 tieu Williams answers the question by show- 

 ing that, when sea-water is evaporated, sul- 

 phate of lime is the first salt to be deposited, 

 while chloride of sodium, sulphate of mag- 

 nesia, chloride of potassium, and the bro- 

 mides, are deposited later. Hence, when 

 the sea-water reaches the point of satura- 

 tion with sulphate of lime, no more can be 

 dissolved in it, but all additional supplies 

 must be deposited. Moreover, if a soluble 

 salt of lime were brought into the sea, its 

 lime would combine with the sulphuric acid 

 there combined with magnesia, or soda, or 

 potash, which would, in obedience to a curi- 

 ous chemical law, leave those bases to com- 

 bine with that one which would form an 

 insoluble compound. Thus the total quan- 

 tity of lime in sea-water is limited by the 

 solubility of sulphate of lime, and this 

 amounts to only about one part in four 

 hundred of water. 



The Caribs and the Greeks. Mr. A. J. 



Yan Koolnijk has published in the " Journal 

 of the Dutch Geographical Society " an ac- 

 count of Carib tombs and relics which have 

 been found in the Island of Aruba, off Dutch 

 Guiana. Among the relics are potteries of 

 good workmanship, elaborately ornamented 

 and painted in a variety of colors obtained 

 on the island. Some of the more common 

 ornaments are figures of frogs and frogs' 

 heads, which indicate that the Indians had 



