December 26, 1884.] 



ffiSOEHBB 



su. 



569 



though it is hoped that an increase in the time 

 may be successfully made at some future day. 

 There is needed a better understanding of the 

 laws which underlie atmospheric changes, so that 

 empirical generalizations may give way to scientific 

 deductions. 



EARTHQUAKES IN THE UNITED 

 STATES AND CANADA. 



" Some say, the earth 

 Was feverous, and did shake." 



Shakspeare. 



The part of the earth's surface occupied by the 

 United States is not generally regarded as much 

 affected by earthquakes. As compared with some 

 other localities, this is true ; yet records show that 

 moderate earthquakes are not so infrequent here 

 as is usually supposed. 



In the twelve years from 1872 to 1883 inclusive, 

 three hundred and sixty-four earthquakes have 

 been recorded as occurring in Canada and the 

 United States, not including Alaska. Their geo- 

 graphical distribution may be expressed in this 

 way. Suppose the country divided into three dis- 

 tricts, — one extending from the Pacific Ocean 

 eastward, to include Idaho, Utah, and Arizona, 

 which may be called the Pacific slope ; the second 

 extending from Montana, Wyoming, Colorado, and 

 New Mexico eastward, to include Ohio, Kentucky, 

 Tennessee, and Alabama, which may be called 

 the Mississippi valley ; and the third, or Atlantic 

 slope, extending eastward again to the Atlantic 

 Ocean, and including the Appalachian region from 

 the St. Lawrence to Florida and Georgia. Then 

 the distribution of these three hundred and sixty- 

 four earthquakes has been 



Pacific slope 151 



Mississippi valley 66 



Atlantic slope 147 



3 6 4 

 These numbers indicate that about once in twelve 

 days an earthquake occurs somewhere in the United 

 States or Canada, and about once a month one oc- 

 curs somewhere on the Atlantic slope. 



It is quite likely, also, that for every earthquake 

 which is of sufficient intensity to get itself noted in 

 the midst of our busy American life, several lighter 

 tremors may have occurred, which, although not 

 violent enough to attract the attention of any one, 

 would yet have left their record on a properly con- 

 structed seismoscope. 



So, if any of our readers feel disposed to set up 

 a seismoscope, they need not be deterred by the 

 paucity of shocks in our country. A seismoscope 

 anywhere along our eastern seaboard, or, still bet- 

 ter, on the western coast, might fairly be expected 

 to record ten or a dozen shocks in the course of 

 the year, and might detect a much larger number. 

 Such observations would be of high scientific 

 value. 



TEMPERATURE AND ITS CHANGES 

 IN THE UNITED STATES. 



"For hot, cold, moist, and dry, four champions fierce 

 Strive here for mastery." 



Milton. 



In the United States the changes of tempera- 

 ture with the seasons are of several types. These 

 are illustrated in the accompanying diagrams, con- 

 structed chiefly from our signal-service reports: 

 the thermometric scale being indicated by marks 

 for every twenty degrees Fahrenheit on the left, 

 and for every ten degrees Centigrade on the right, 

 of each local division. The middle horizontal line 

 shows the measure of that arithmetical abstraction 

 commonly known as the mean annual temperature : 

 and the adjoining lines above and below indicate 

 how much variation there may be in the means of 

 different years. In this respect, St. Vincent, Minn., 

 has a much more irregular climate than Key West. 

 The dots connected by a fine, dotted, curved line, 

 represent the mean monthly temperature, begin- 

 ning with October on the left side, descending to the 

 January minimum, crossing the mean annual line 

 about April, on the way to the July maximum, and 

 descending again to October on the right margin. 

 In illustration of the least annual variation, a curve 

 is introduced for the equatorial station of Singapore, 

 at the extremity of the Malay Peninsula, where the 

 mean annual change is only seven degrees (F.); 

 and, in contrast with this torrid uniformity, we find 

 Yakutsk, Siberia, in the so-called temperate zone, 

 giving the greatest known annual variation, on 

 account of being far north, and far within a great 

 continental region. St. Vincent, the coldest of the 

 signal-service stations, is probably our nearest ap- 

 proach to this extreme variability. 



The irregularity of the monthly means in differ- 

 ent years is shown by short transverse lines above 

 and below the dots : these are farther apart in 

 winter than in summer, on account of the frequency 

 of winter storms which produce great and sudden 



