SCIENCE. 



[Vol. XV. No. 36 . 



practical ; yet I think I will speak of it, as I see no reason why 

 it could not be applied with success, and still further increase the 

 eifectiveness of the rajige-finder. The object is to make the 

 range-iinder self-recording, to automatically adjust the balance, 

 and to avoid the need of a third operator. The method is ex- 

 tremely simple. First, the ' ' slider ' ' is provided with a nut 

 •thi-ough which a spindle revolves, the spindle being the continu- 

 ation of a small motor-shaft. The fields are wound with two 

 coils in such a manner, that, when the circuit is closed through 

 one, the motor revolves in a particular direction, and, when closed 

 through the other, in the opposite direction ; moving the slider 

 backward or forward, as the conditions might require, to estab- 

 lish the balance. The motor is fed from one cell of storage or 

 other battery, at about two volts potential. 



The operating mechanism is equally simple. Two small mag- 

 nets, A and B, are connected to the same cell that supplies the 

 motor, and the return wire of each terminates in a drop of mer- 

 cury, A and B', located each side of the galvanometer-needle, 

 ■so that the least movement to one side or the other will cause 

 contact with the globule of mercury. The circuit thus being 

 closed tlu-ough the needle to the other pole of the battery, the 



-con-esponding magnet becomes energized, attracting the armature, 

 which closes the corresponding circuit of the motor. The object 

 of the magnets A and B is to reduce the sparking at A' and B', 

 -and they might possibly be dispensed with. They were to be 

 wound with considerable resistance, that the current might be 

 so small as to prevent any ti-ouble at A' and B' by burning or 

 -sticking of the contacts. 



There are other arrangements whereby the above result might 

 JDe accomplished, but I send this, as it may be of some interest 

 "should this plan of automatically adjusting the balance not have 

 ieen previously thought of. J. F. Denison. 



New Haven, Conn., Feb. 15. 



given to Dr. Stockbridge, and not to the author. When I use 

 the facts of Dietrich, Hoffman, Liebenberg, or any other man, 

 and I give him credit, my duty ends then : Dr. Stockbridge ha 

 no claim to them, even though he may have translated them. 



The statements in the eight pages referred to are commonplace, 

 and are found in any good modern text-book that treats of the 

 subject. 



Niti-ification is described in great detail in Part II. of the 

 third supplement to Watt' s ' 'Dictionary of Chemistry' ' (p. 1397) ; 

 also in Bloxam's "Chemistry" (p. 173) and Storer's "Agri- 

 culture" (vol. i. p. 398). The word "microbe" ("little life") 

 was first used by Sedillot. The latest investigators are Warring- 

 ton, Schlosing, and Mtintz. The per cent of ash in plants is 

 given in ' 'How Crops Grow, ' ' by Johnson (p. 30) ; ' 'How Crops 

 Feed, ' ' by the same author (p. 364) ; ' 'Chemistry of the Farm, ' ' 

 by Warrington (p. 2). " Asohen Analysen Von Landwirthschaft- 

 liche Prouducten," by Wolff, gives 5 per cent of ash. "The 

 Geological Survey of Ohio, 1870," p. 368; the average of 151 

 analyses, gives 4. 84 per cent of ash. It has been thought that the 

 transpiration of plants has been worked out in greater detail than 

 any other siibject. Nearly every possible condition has been 

 investigated by some one. The law of transpiration from the 

 upper and lower portions of the leaves has been worked out by 

 Guettard, Unger, and Bonnet. Tlie relation between the num- 

 ber of stomata and the rapidity of transpiration has been experi- 

 mented upon by Von Hohnel and Garreau ; the amount in wet 

 and dry weather, by Moldenhawar ; the effects of light and dark- 

 ness, by Wiesnar and Van Tieghem; how transpiration is in- 

 fluenced by the liquid absorbed, by Senebier, Sachs, and Bur- 

 gerstein ; the pressure in the growing plant during transpiration, 

 by Meyen, Sachs, and Von HSlmel ; even the effect of the differ- 

 ent rays of the sun, by Wiesner ; and the age of the leaves, by 

 Hohnel and Deherain. The amount of water transpired for 

 wheat, barley, oats, beans, red clover, rye, peas, etc., has been 

 determined by Hellriegel, while Sachs, Hofmeister, and Hales 

 have determined the amount ti-anspired fi-om the giape-vine, sun- 

 flower, cabbage, etc. 



Tlie facts about the fineness or division of soil are stated in 

 Williams's "Applied Geology" (p. 111). In "Chemical Bulle- 

 tin, No. 10, Department of Agriculture, ' ' under the head (p. 10) 

 "The General Fertility of Soils depends Principally on Their 

 Texture," is the following language: "These qualities depend 

 altogether on the state of division of the soil and of its geological 

 origin' ' (see ' 'Soils of the Farm, ' ' by Scott and Morton) . When 

 the same statement has been made by so many authors, it is 

 difficult to state positively the source of information ; but in two 

 instances I had the references marked. 



In Dana's "Manual of Geol- 

 ogy," 1879, p. 714, this lan- 

 guage is found: — 



Soils and Alkali. 



Please gi'ant me the use of your paper to reply to the article 

 by Dr. Stockbridge in your issue of Jan. 17, on soils and alkali. 

 "When the bulletin was written, it was thought best to preface it 

 "with some general statements about soils. With this end in 

 view, I collected, condensed, and arranged, from the sources at 

 my command, the facts of the first eight pages of the bulletin. 

 There never has been any claim made to originality in these 

 -eight pages. The facts were collected simply to make the bulle- 

 tin more intelligible to the farmers. As far as I knew, I tried to 

 give credit to every one for his work. The domain of science is 

 too large, and human life is too short, to have any one mind 

 even comprehend it. It was explained to Dr. Stockbridge that I 

 did not collect all the material myself, and, if any of the matter 

 was his, due credit would be given him. This should convince 

 ■any man that I acted in good faith in tlie matter. He makes 

 some very broad assumptions, that are not warranted in this day, 

 age, and generation : 1st, That he has a patent right on German 

 and other foreign publications, and that no one else has access to 

 them ; 2d, That no one else can translate them ; 3d, If he trans- 

 lated them, and any one afterwards uses the facts, credit must be 



The earth has three 

 sources of heat: (1) The 

 heat of the earth's interior; 

 Gal and mechanical action. 



prominent 



in; (3) The 



3) Chemi- 



He quotes me: — 



O'BRINE (p. m. 



The heat comes from three sources: 

 Solar heat, as the sun's rays; heat of 

 chemical decomposition -within the 

 soil, and the original heat of the earth's 

 interior. The latter cannot be of any 

 value to plants; the heat of chemical 

 decomposition is not of any value, ex- 

 cept in a few special cases. The sun, 

 therefore, remains the only source of 

 heat of practical importance in rela- 

 tion to the production of crops from 

 the soil. 



In making the application of these facts to plants, what other 

 conclusion could be arrived at? 



He quotes me: — 



O'BRINE (p. 4). 



Oats, rye and buckwheat thrive with 

 the lowest amount of organic matter, 

 requiring from one to two per cent. 

 Wheat and tobacco seem to require 

 most among the common agricultural 

 products, and do their best upon soils 

 containing from five to eight per cent 

 of organic matter. 



The text-book of geology by 

 Geikie, 1885, p. 326, in speak- 

 ing about the organic matter in 



soils, says, — 



It is the experience of practical agri- 

 culturists in Britain that oats, rye, 

 will grow upon a soU with one and one- 

 half per cent of organic matter, but 

 that wheat requires from four to eight 

 per cent. 



I added to the statement in the geology, "buckwheat and 

 tobacco ;" the one being proverbial for gi-owing on poor soil, and 

 the other for requiring a rich soil. The order of arrangement 

 that I used is found in Loudon's ' 'Encycloptedia of Agi-iculture, ' ' 

 eighth edition. 



