46 C\ Dewey on Caricograj>}iy, 



by a binding-screw ; over this a rod of platinum is secured in. 

 the same manner to a spring which presses them together; an- 

 other spring loaded acts like a hammer upon the end of the 

 first spring, to separate^ the phitinum rods. A ratchet wheel 

 j^resses down this spring hammer, and allows it to recoil and 

 strike the other spring. Bj this the interruption is more instan- 

 taneously made, and the distance to which the platinum rods 

 are separated easily regulated. This point appears to be of im- 

 portance. The spark is lessened if the platinum rods are sepa- 

 rated farther than actually to break their contact. The usual 

 primary helix of large wire and the interior bundle of iron wires 

 are placed within the glass tube. 



In my last instrument, I used a tube closed at the top, more 

 effectually to cut off the passage of tlie current from one end to 

 the other, through the primary helix or iron wires. I have used 

 a Bunsen's battery of four to six cells; four give the spark of 

 as great length, but a few more cells increases the volume. I^ 

 have applied a battery of eighteen cells and also a plate battery 

 of fifty-six pairs without endangering the coil. The instrument 

 is undoubtedly capable of being greatly increased in size and 

 power. 



Boston, 5fay 2, 1857. 



Art. y. — Caricography ; by Prof. C. Bewey. 



(Continued from vol. xix, p. 266, Second Series.) 



No. 250. Carex Dovylasn^ Boott, in IToolv. Fl. Bor.-Amer. 



Spica oblonga eomposita, intcrdiim dioica; spiculis miilti^ 

 8-14 ovatis dense aggregatis supern^ squamo-bracteatis, distig- 

 maticis; fructibus ovali-lanceo]atis bifidis vel bidentatis margins 

 ciliatis, sqnamam lanceolatam castaneam non-aequantibus. 



Culm scarcely a foot bigh^ erect, briglit green, leafy towards 

 the base but naked above ; spike compounded of many ovate 

 spikeletSj 8-14, closely aggregated above, less so below, and 

 tlie lowest sometimes branched, sometimes all pistillate and sta- 

 mens on another plant; stigmas two; fruit ovate-lanceolate, 

 plano-convex, rostrate, bidenlatc, subscabr.ous on the margin, 

 and a little shorter than the lanceolate and tawnv scale. 



West of Fort Pierre, Nebraska Ten ; collected by Dr. F. V* 

 Haydcn in his important geological explorations there. These 

 specimens are not quite so large or the spikes so long as those 

 mentioned by Dr. Boott from the northwest coast and Bocky 

 Mountains. This species, like G. Ricliardsoni^ R, Brown, has 

 found a habitation far south of the one orimnallv discovered. 



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