512 



SCIENCE 



[N. S. Vol. XXVI. No. 668 



Engineering. 



This reduces the number somewhat and includes 

 one subject not included in your classiiication. 

 I believe that the time has come when we must 

 have technical journals in subjects pertaining to 

 agriculture just as they have in all other branches 

 of scientific work. 



Professor J. W. Gilmore writes: 



This scheme seems to me eminently feasible and 

 I believe is a distinct step in arranging and sys- 

 tematizing our station literature. I would like 

 to hear a discussion, however, along three lines 

 at least: 



1. Scheme of classification. 



2. Whether station workers might not receive 

 any or all of the series free on request. 



3. What may be the attitude of the now-estab- 

 lished scientific journals toward the scheme. 



Would it be well to invite discussion along 

 these lines? 



The methods and means of publication for 

 scientific station matter is a subject in which 

 all experiment-station investigators are vitally 

 interested, and the writer has thought it de- 

 sirable to publish his thoughts on the subject, 

 hoping to stimulate a general discussion out 

 of which sentiment may crystallize so that 

 some advanced step may soon be taken by the 

 station authorities. 



H. J. Webber 



CoRireij. Univeesitt 



ON THE EFFECTS OF MAGNESIUM SULPHATE ON 

 PLANTS 



In the issue of Science of August 16, Pro- 

 fessor William J. Gies publishes a letter, in 

 which my refutation of an unjust attack is 

 subjected to an analysis which I cannot regard 

 as going to the essential point. I must, there- 

 fore, once more and more distinctly state that 

 my inferences as to the poisonous action of 

 magnesiurn sulphate on plants can, of course, 

 only relate to the conditions of my experiments 

 and that I nowhere have made the assertion 

 that these poisonous actions would he ohserved 

 also at still higher dilutions than those I had 

 used, for I was very well acquainted with the 

 truth that the action of a poisonous substance 

 decreases with the dilution and that beyond a 

 certain dilution even a stimulating action can 

 take place. 



I have further pointed out that the poison- 

 ous effects of that salt are modified by the 

 lime content of the cells; the more lime there 

 is present in the cells, the more magnesium 

 sulphate will be required to exert a poisonous 

 action. From this standpoint my own obser- 

 vation on the stimulating action of magne- 

 sium sulphate' under certain conditions, be- 

 comes intelligible. 



Oscar Loew 



SPECIAL ABTIOLEa 



THE SPARK OHRONOSCOPE 



Eight years ago I published a description 

 of a new ehronoscope in a technical mono- 

 graph. Eight years of continued use, in 

 which the instrument has been tested for con- 

 venience, durability, adaptation and accuracy, 

 give such assurance of satisfaction that I am 

 moved to bring the instrument to the atten- 

 tion of a wider circle of scientists through the 

 columns of this journal. I would especially 

 invite comparison with other instruments on 

 the three fundamental qualities of accuracy, 

 economy in operation and adaptability. 



The following brief description is essentially 

 an extract from the original account in The 

 University of Iowa Studies in Psychology, 

 Vol. n., p. 155 if. 



Of the hitherto known forms of apparatus 

 for measuring short intervals of time, the 

 graphic spark apparatus is the most accurate 

 and the pendulum apparatus the most con- 

 venient. In the ehronoscope that is shown in 

 the accompanying figure, the spark method of 

 recording is combined with the pendulum 

 action. 



The cut is reduced to a scale one sixth of 

 the size of the apparatus. The pendulum is 

 shovm in the starting position. The lower bob 

 terminates in a knife edge which rests upon 

 the projecting edge of a mechanical release 

 key. The action of this key is soundless and 

 gives the pendulum no impetus in either direc- 

 tion. On the other side of the apparatus is a 

 spring key which catches the pendulum at the 



• Cf. " Flora," 1893 ; observations on the g^o^vth 

 of the roots of Tradescantia, in my article on the 

 " Physiological Functions of Lime and Magnesiai." 



