Decembeb 28, 1883.] 



SCIENCE. 



823 



not also just. It would appear, not only tbat tliis dog 

 must have thought her plan through, but that she 

 must also liave held it definitely in mind for several 

 days while she executed it, thus indicating quite un- 

 equivocally, it seems to nie, that one animal at least, 

 ranked lower than man, possesses the power of look- 

 ing into the future and of executing plans deliberately 

 laid with reference thereto; " man is the only animal 

 which lias the power of looking into the future," to 

 the contrary notwithstanding. F. H. Kix<i. 



Rivor Falls," Pi.rce county, Wia? 



Method for making electrical signals. 

 When I first became connected with the Alabama 

 agricultural and mechanical college, the recitation 

 signals were made by means of electric bells, one in 



each professor's room. These were rung separately 

 by pressing in succession as many push-buttons as 

 there were bells. In order to complete the system, 

 it was necessary to have one wire for each bell, and 

 a return-wire running through the whole length 

 of the system; and therefore only one bell could be 

 rung at once. In the circuit there were twelve bells, 

 about one-half mile of wire, and twelve one-gallon cells 

 of Watson's battery. One of the cadets of the college 

 was delegated to sound the signals at the end of each 

 fifty minutes, which was the length of the recitation 

 liours. Sometimes he would ring too soon, .ind at 

 other times several minutes too late. This was fre- 

 quently annoying, particularly when an interesting 



be made to strike twice any multiple of five minutes. 

 .\fter adjusting tUis clock so .as to make it strike every 

 fifty minutes, 1 insulated it on a square of plate glass. 

 I then made an oblong opening in the side of the wood- 

 work about one inch long. This slit was made on a 

 line with the ball of the striker. Through this hole I 

 passed a copper wire, and fastened it securely to the 

 hammer of the gong. In the eml of the wire outside 

 of the clock I made a loop, as shown at ^1, Fig. 1. 



A second wire, ^1 li (', was attached to the first, as 

 shown in the figure. A loop at li fits in a slit in the 

 upright D, and a pin is inserted at li to hold the wire 

 in position and at the same time allow the ends A and 

 C to work up and down when the hammer of the 

 clock strikes. The bottle C K is partly filled with 

 mercm-y. From this mercury-cup a wire, E W, runs 

 to one pole of the battery. The other pole con- 

 nects at /i with the wire It', after passing through 

 all the bells of the system. S is a weight to 

 counterbalance the arm B C. It will be readily 

 seen that the outward stroke of the hammer will 

 throw the end of wire A B C into the mercury, 

 thus completing the circuit, and causing all the 

 bells to ring. The blow of the hammer against 

 the gong of the clock will raise the end C, and 

 break connection. All but one of the bells must 

 be single stroke: otherwise it will be impossible 

 to obtain satisfactory results. By using one bell, 

 with attachment for breaking and closing the 

 circuit, the ringing will continue as long as the 

 wire at C is in contact with the mercury. 



The above system has been in operation for 

 one year, and lias given satisfactory results. 

 It has occurred to me that our large bell, weigh- 

 ing nearly two thousand poun<ls, can be made to strike 

 the hours for the benefit of the town by placing it in 

 the system just described, with the following adjust- 

 ment. Procure a soft iron horseshoe magnet si.K or 

 eight inches long, and secure it at M on the iron rod 

 A 1) C, Fig. 2. This becomes magnetized when the 

 clock completes the circuit. The armature J' Y is 

 attracted, and the ball X strikes the bell. The elas- 

 ticity at E raises the ball immediately from contact, 

 and allows a clear and distinct ring. The tension- 

 spring T raises the armature from the magnet, and 

 the current ceases to flow. If it is desirable at any 

 time to ring the bell in the ordinary way by means 

 of the rope B, the adjustment of the system may be 

 sustained by making the supporting rod A D C secure 

 to the bell-shaft it ,1. and thus permitting the mag- 

 net and fixtures to swing with the bell. 



P. n. Mem., Jun. 

 Auburn, Al.i. 



and important lecture w.is in progress. In the at- 

 tempt to obviate this difficulty, the plan that I am 

 about to describe was suggested to my mind. 



We have an excellent compensated clock that can 



GEIKIE'S GEOLOGY. 



Tert-bnok of geology. By Aiichibald Gkikie, 

 LL.U., F. Ills., director-general of the Geological 

 suiTey of Great Britain and Ireland, etc. Witli 

 illustrations. London, Macmillan ^, Co., 1882. 

 971 p. 8°. 



Text-books in science once lield a luthcr 

 low place ill the estimation of scientific men. 

 Labor of this sort was long relegated to the 

 book-makers, who, copying statements and il- 

 lustrations one from another, gave the student 

 more of the errors of by -gone days than of the 

 knowledge of their own. But in our own time 

 all this has been greatly t)ettered. Xi»w a man 



