February 19, 1892.] 



SCIENCE. 



109 



soulhein hemisphere to cool the ocean waters and still further 

 lower the temperature of the Gulf Stream, and also the tropical 

 currents of the oceans, including the great Japanese current, the ice 

 period of both hemispheres would be brought about during the 

 same era. For it is well known to those who have studied the 

 subject that the Gulf Stream derives a large portion of its heat 

 from the south Atlantic; which would not be the case should the 

 waters of the southern hemisphere be chilled by ice. For it ap- 

 pears that all of the south Atlantic islands during frigid times were 

 burdened with glaciers. Even the island of St. Helena, situated 

 in the tropical zone, has the appearance of having been heavily 

 iced during some remote period. Its steep ravines, which deepen 

 as tliey approach the sea, recall to the southern voyager the ice- 

 worn islands of the higher latitudes. Thus when the temperate 

 regions of both hemispheres were heavily iced the tempei'ature of 

 the tropical seas must have been comparatively low, especially on 

 the eastern sides of the oceans which are swept by the polar cur- 

 rents. Moreover, the sea was much Salter than now, on account 

 of a large portion of its waters being absorbed by glaciers. Fur- 

 thermore, whenever the arctic channels are filled with glaciers the 

 independent circulation of the arctic waters must cease; conse- 

 quently the Gulf Stream, raeeting with less opposing polar cur- 

 rents on its sweep northward, would thus be able to gain a much 

 higher latitude than now. Although its waters at first would be 

 colder than they are to-day ; still their superior saltness would add 

 to their ability for dissolving ice wherever they were able to flow. 

 But it appears that the Gulf Stream and other tropical currents of 

 the northern oceans would not be able to subdue the cold accu- 

 mulated in northern ice sheets without the assistance of a com- 

 paratively warm ocean in the southern hemisphere. The southern 

 seas being so much superior and so widely connected with the 

 northern, the tropical currents of the latter seas would require 

 the assistance of the southern oceans to subdue the cold of a 

 northern ice period, in the same degree that it required their co- 

 operation to briog about the frigid period. The arctic straits, 

 which now facilitate the independent circulation of cold Arctic 

 waters, would, when filled with glaciers, be slow to thaw out, even 

 with the increasing warmth of the arctic regions, on account of 

 being situated to the windward of the warm gulf currents. There- 

 fore, the glaciers that filled their deep channels would be the last 

 great body of ice to melt in the northern regions; and for this 

 reason it is probable that there are fragments of the old ice of the 

 last frigid period still unmelted and now form a portion of the 

 lower shores of the arctic straits. This conclusion is in har- 

 mony with reports from Point Barrow which inform us that a 

 stratum of pure ice is found beneath the scanty soil. The low 

 temperature of the waters of the tropical oceans during the per- 

 fection of a frigid period must have been very destructive to 

 oceanic life; while such as survived probably found refuge in 

 nearly landlocked equatorial seas, where the waters were largely 

 excluded from the colder ocean, and also freshened by such rivers 

 as emptied into them. Meanwhile, the low temperature of the 

 ocean must have chilled the atmosphere over the land to such a 

 degree as to have caused the destruction of many species of ani- 

 »""'■= C. A. M. Tabee. 



The abstract under the above title lu o„ 



which I have only just found time to read, proves very interest- 

 ing to me, and I do not wish in any way to have it inferred that 

 I disbelieve in the influence of electricity, at least indirectly, upon 

 the growth of plants; but it does not seem out of place to call at- 

 tention to the fact that the comparative rarity of mildew on plants 

 Krown above electricity-bearing copper wires in moist soil may be 

 due to the action of the copper salts formed in killing the mildew 

 rather than to electrical action. 



The roots of the lettuce in the experiment mentioned at " Gar- 

 den A " {Science, p. 36) are stated to have ' ' grown about the 

 wires, as if there they found the greatest amount of nourishment," 

 etc. This would also be the result from the roots seeking the en- 

 vironment best suited for growth, if the mildew could not thrive 



about the wires on account of the trace of copper salts which the 

 soil contained. 



The use of sprays containing copper salts, in the form of Bor- 

 deaux mixture or similar compounds, as a preventive of mildew 

 of grape-vines and other plants is well known, and the control 

 plot, "Garden B," should have been provided with copper wires, 

 exactly as was "Garden A," to make the results of the experi- 

 ment conclusive. As I have not seen the original article in the 

 Bulletin of the Hatch Experiment Station, from which the abstract 

 in Science was taken, it may be the fact that this action of the 

 copper salts upon mildew has been discussed there. 



George Dimmock. 



Canoble Lake, N.H., Feb. 15. 



AMONG THE PUBLISHERS. 



E. & F. N. Spon & Co. announce "Roll Turning for Sections 

 in Steel and Iron," by Adam Spencer. The subject of roll- turning 

 is treated from a purely practical point, and for practical men. 

 The drawings are the result of experience, and their value consists 

 in the fact that they are working drawings, that is, drawings of 

 rolls which have passed through the ordeal of actual work. The 

 arrangement of the work is as follows: First, drawing of modern 

 blooming for steel slabs, followed by a pair of billet rolls, then 

 various sections showing the related grooves in cogging, roughing, 

 and finishing rolls, with the position and character of collars re- 

 quired. " A Text-Book of the Science of Brewing," by Edward 

 Ralph Moritz and George Harris Morris. The following extract 

 from the introduction will show its character: "The object of 

 this work is to provide in a convenient and accessible form such 

 knowledge of the processes of brewing and of the materials em- 

 ployed in that industry as is at our disposal; and — so far as we 

 are able — to connect such knowledge with the practice of brew- 

 ing. We therefore intend it as a text-book in which may be found 

 the results of scientific research together with the practical con- 

 clusions which we consider justly deducible from them. We do 

 not pretend that a perusal of our work will enable a novice to 

 brew beer; neither will a study of it convert a purely practical 

 man into a chemist. It is meant, however, to lead the brewer to 

 a better understanding of what we may term the physiology and 

 pathology of brewing, and, by so doing, put at his disposal a means 

 for more efiScient control over his operations." "Manual of In- 

 struction in Hard Soldering," by Harvey Rowell. "The Mechani- 

 cal and Other Properties of Iron and Steel in Connection with 

 Their Chemical Composition," by A. Vosmaer, engineer. The author 

 has gathered together the widely scattered information on this 

 important subject, and gives in brief outline the actual knowledge 

 of the intimate connection that exists between the properties of 

 steel and iron and their chemical composition. The elements — 

 carbon, manganese, silicon, phosphorus, sulphur, copper, chro- 

 mium, titanium, tungsten, aluminium, nickel, cobalt, arsenic, anti- 

 mony, zinc, lead, tin, silver, molybdenum, vanadium, potassium, 

 sodium, barium, strontium, calcium, and magnesium — have 

 been considered separately and in the following manner : First, as 

 to the metallurgical behavior of the elements in question; next, 

 to deal with their influence on pig iron, cast iron, wrought iron, 

 -•^ steel; lastly, the special uses made of them, and their occur- 

 ■^"nufactured objects. The gases, intermolecular, reac- 

 •lave been carefully considered, and analyses 

 issemer, basic, and forge pig-irons, spiegel- 

 \x^^. 3f , ferrosilicons, ferrochromes, ferrotungsten, 



ferroalumiix. it-irons, weld irons. Steel — railway material, 



structural steel, ordnance material, miscellaneous. With a dia- 

 gram of silicon in cast iron, and of disappearance of carbon. 

 Also a new edition of " A Practical Treatise upon Warming Build- 

 ings by Hot Water." 



— Morris Phillips of the Home Journal goes abroad every su*"- 

 mer for recreation and business. He has kept up that habit for 

 nearly twenty years, besides travelling widely over this coui'ry, 

 and as a result of his experiences he has just compiled a note- 

 book of practical hints for tourists entitled " Abroad S'l'd at 

 Home," in which he gives incidents of his travels, as we U as a 



