May 2, 1878] 



NATURE 



over this great plateau presents' theai as direct] obstruc- 

 tions to the eastward movement of storms, and their 

 influences on the latter are very marked. Indeed the 

 most interesting study in American meteorology is that 

 of the modifications produced by the great mountain 

 plateau of the west, or the disturbances passing over it. 

 The sub-area of the plains is that in which some of the 

 most remarkable phenomena of storms are observed. 

 The valleys of the Mississippi, Missouri, and Ohio, and 

 the basins of the lakes and Gulf of Mexico are the 

 theatres of tremendous storm movements, and are con- 

 sequently the favourite areas for observation chosen 

 by American meteorologists. Within them are ex- 

 perienced nearly every type of storm that traverses 

 the Atlantic toward Europe. Unlike the sub-area 

 of the mountains to the westward, that of the plains 

 is favoured with an abundant rainfall which renders the 

 great expanse fertile in nearly all its sections. The 

 growths of the tropics flourish in the south, and produc- 

 tiveness marks its various climatic zones until the vast 

 pine forests of the north define 'the agricultural limits. 

 The contrast between the two sub-areas is extraordinary, 

 yet their widely different conditions are easily accounted 

 for when their respective meteorological aspects are 

 studied. The Gulf of Mexico, with its accumulation of 

 tropical waters, plays a very important part in creating 

 the prevailing weather conditions of the sub-area of the 

 plains. From it flows a continuous current of warm 

 humid air, which supplies moisture and energy to the 

 storms that descend from the regions of the north-west 

 into the great river valleys. It is the cradle of the equa- 

 torial current that sweeps across the ocean far into the 

 Arctic seas, carrying warmth and verdure to latitudes in 

 Europe far north of the general habitable limit on the 

 American continent. But it is unnecessary to do more 

 than refer to so familiar a region in describing briefly 

 the natural subdivisions of the field of observation. 



For the Atlantic, like the Pacific, we have the dividing 

 line of the equatorial current of the Gulf Stream. North 

 and west of that line the surface temperature is low, 

 south and east of it very uniform, and along it high. Air 

 in motion over these surfaces is consequently affected by 

 rapid variations of temperature, which affect in turn the 

 energy of the disturbances traversing the atmospheric 

 volume. 



A very marked effect of this kind is produced when 

 storms leave the Nova Scotia coast, and at once com- 

 mence to pass over the equatorial and Polar counter 

 currents. The pressure falls rapidly, and great gales are 

 induced, but the storm seems to be held for several hours 

 over the region between Nova Scotia and Newfound- 

 land, as if controlled by forces which it strove to over- 

 come. When fairly past Cape Race the movement of 

 the storm is no longer interrupted by the influences of 

 the currents, and makes a very uniform progress towards 

 Europe. When cyclonic storms reach the Florida or 

 Carolina coasts from the Gulf of Mexico their energy 

 seems to be increased when passing over the Gulf 

 Stream, but their courses are not altered very much by 

 the influence of that current. This is probably due to 

 its narrowness when passing along the coast to latitude 

 35°. Eastward of the Gulf Stream, and over the oceanic 

 region of uniform surface temperatures the energy of the 



storms decreases somewhat, and the areas of their depres- 

 sions increase. But on approaching the west coasts of 

 Europe the storms again resume their forces and deposit 

 heavy rains. Europe, like America, is divisible into two 

 sub-areas, one of mountains and the other of plains. The 

 eastern limit of the former is that of a line following the 

 Scandinavian Mountains toward the Alpine development 

 into Saxony, thence following the Carpathian mountain 

 outline, and passing southward over Bulgaria and the 

 Balkans to the Syrian mountains. The irregularity of 

 such a dividing line is very apparent, but we may assume 

 that given to be correct enough for our purposes. In 

 crossing the Scandinavian Mountains, Atlantic storms 

 invariably deposit a great rainfall over Norway and pass 

 into the Gulf of Bothnia and Eastern Russia with a 

 reduced precipitation. When on the great Muscovite 

 plains the storms again increase in area, just as they 

 do in the valley of the Mississippi after crossing 

 the Rocky Mountains in Montana; the break in 

 the dividing-line between the sub-areas of mountain 

 and plain in Europe represented by the Baltic and 

 the low lands of Northern Germany, forms a storm gate- 

 way to the interior plains, which is frequently passed 

 by Atlantic disturbances. The mountain systems of 

 Switzerland, Italy, and the Balkan peninsula, perforn^ 

 important parts in modifying the conditions during storm 

 movements in Northern Europe, and have each their 

 peculiar local influences on the weather. If these moun- 

 tains did not form barriers between the regions of great 

 evaporation with their humid winds from the south, and 

 those of Northern and Central Europe, a parallel 

 between the meteorological phenomena of the Missis- 

 sippi Valley and those of Eastern and Southern Russia 

 in Europe could be drawn very easily. Having now 

 roughly sketched the field of observation at present 

 available, and suggested here and there a few points 

 worthy of special consideration, I will endeavour in the 

 next article to explain how storms move over the several 

 sub-areas, and the changes they undergo in each. 



Jerome J. Collins 

 {To be coniimted.) 



NEWCOMB'S ASTRONOMY 

 Popular Astronomy. By Simon Newcomb, LL.D., 



Professor U.S. Naval Observatory. (London: Mac- 



millan and Co., 1878.) 

 A WORK on popular astronomy by an author so 

 distinguished in the higher branches of the science 

 as Prof. Newcomb, will be welcomed with more than 

 ordinary interest. The main object of the present 

 volume is to present the general reader with a con- 

 densed view of the history, methods, and results of 

 astronomical research, especially in fields of most popular 

 and philosophical nature at this epoch, in such language 

 as to be intelligible without mathematical study ; it has 

 not been designed to instruct either the professional 

 investigator or the special student of astronomy. 



In his first chapter the author briefly treats of the 

 phenomena of diurnal motion, the motion of the sun 

 amongst the stars, the precession of the equinoxes, of 

 the moon's motion, and of eclipses of the sun and moon, 

 concluding with some account of the calendar. In his 



