THE INTERNATIONAL WEATHER-SERVICE. 307 



Now, with such clear barometric and thermometric conditions in and 

 around Great Britain, a " cold, wet summer " in 1879 was almost inevit- 

 able, and a prediction to that effect, based on the simultaneous inter- 

 national data, would have been justifiable. Of course, new conditions 

 might arise late in June, but the conditions prevalent, according to all 

 physical probability, authorized such a forecast at the commencement 

 of the summer, and would have been of incalculable value. Ask the 

 British farmer what he would have freely paid in June to have gained 

 some idea of the July weather ! Or ask the English merchant what 

 he would have freely given in June for a tolerably correct crop-fore- 

 cast for the summer of 1879 ! Yet this is no hypothetical case, but 

 one familiar to all, involving a whole nation in agricultural and finan- 

 cial distress, against which, with international reports from the Faroe 

 Islands and Iceland, it could have been forewarned. 



The collection of the "international" cloud-observations — especially 

 those taken at sea — opens one of the most fertile and fascinating fields, 

 not only for the elucidation of the profoundest atmospheric problems 

 by the theoretical scientist, but for the popularization of meteoric 

 knowledge. The clouds are Nature's weather-guides, at all times 

 serving to preannounce the approach of storms, or the return of clear 

 weather. Until the middle of the seventeenth century (when Torri- 

 celli's experiments led to the invention of the barometer), and long 

 after, the clouds furnished the only weather-indications which the 

 world had. And, the more modern meteorology is developed, the 

 more do the ablest of its leaders seek to understand these unen-ing 

 monitors of every weather-change. Varied as they are, their forms 

 may be reduced to two or three types, so defined and imposing that 

 the most unscientific can learn to recognize them and construe their 

 meaning. The international observers enter on their blanks the amount 

 and direction of clouds. " The most valuable of weather-signs," says 

 Mr. Ley, " are obtained not so much from the shape of the clouds as 

 from the directions from which clouds of different levels are observed 

 to travel, and it is these weather-signs which, in the present state of 

 our knowledge, can be most readily reduced to definite rules." 



Take a single illustration of the utility which such rules would 

 have for the farmer, the sailor, or any close observer of the sky. Our 

 storm-centers are generally preceded by a great bank of those clouds 

 to which the name cirro-stratus is given. They are composed largely 

 of freezing or frozen vapor, floating at great elevations, and often very 

 far in front of the depression and over the belt of country which is to 

 receive its rainfall. They move in parallel lines, and are distinguished 

 by their thread-like and attenuated delicacy, as well as by their alti- 

 tude — from 20,000 to 40,000 feet — from all local clouds. Outlying 

 streaks of the cirro-stratus, frequently visible from twenty to one hun- 

 dred miles in advance of the main pack, " like pioneers of the coming 

 army," can easily be detected. But the main body, since it forms the 



