H6 ANNUAL OF SCIENTIFIC DISCOVERY. 



This -well-known fact of the lower mean temperature of places of 

 greater altitude has led to the strangest hypotheses. The sun's rays 

 were not supposed to contain all the conditions for warming a body, 

 but to set in motion the "substance 1 ' of heat contained in the earth. 

 This "substance 11 of heat, cold when at rest, was attracted by the 

 earth, and was therefore found in greater abundance near the center 

 of the globe. This view, it was thought, explained why the warming 

 power of the sun was so much weaker at the top of a mountain than 

 at the bottom, "and why, in spite of his immense radiation, he retained 

 his full powers. 



This belief, which especially prevails amongst imperfectly* informed 

 people, and which will scarcely succumb to correct views, is directly 

 contradicted by the excellent experiments made by Pouillct at differ- 

 ent altitudes with the pyrheliometer. These experiments show that, 

 everything else being equal, the generation of heat by the solar rays 

 is more powerful in higher altitudes than near the surface of our 

 globe, and that consequently a portion of these rays is absorbed on 

 their passage through the atmosphere. Why, in spite of this partial 

 absorption, the mean temperature of low altitudes is nevertheless 

 higher than it is in more elevated positions, is explained by the fact 

 that the atmosphere stops to a far greater degree the calorific rays 

 emanating from the earth than it does those from the sun. 



REMARKABLE PLUMB-LINE DEFLECTION AT COWHYTHE, 



SCOTLAND. 



The Banffshire Journal, Scotland, publishes the following statement re- 

 specting a curious local disturbance of the plumb-line, in the vicinity of 

 Co why the, now under the process of investigation by Sir Henry James, 

 Superintendent of the British Ordnance Survey. It says : 



Early during the present century the headland eastward of Portsoy 

 on Cowhvthe was visited by an officer of the Royal Engineers with the 



* > 



zenith sector, constructed for the Ordnance survey of this country by the 

 celebrated R im-den, and from the observations made with that instru- 

 ment to determine the latitude of the trigonometrical station there, it W;M 

 found that the plumb-line, instead of being vertical, was deflected north- 

 ward of the zenith and southward of the earth's center fully 9" of angu- 

 lar measure. This extraordinary and unexpected result was viewed with 

 great interest by the scientific world, especially by such as were employed 

 by their respective governments in connection with the determination of 

 the figure of the earth; and, by way of verification, a party of the same 

 corps, some 16 years back, furnished with a new zenith sector, designed 

 by the present Astronomer Royal, and constructed by Troughton and 

 Sims, visited the same spot. More observations, and to a greater number 

 of stars, resulted in confirming the first or earlier determination, and here 

 the matter rested, merely as a subject of occasional wonder to those con- 

 cerned, till recently the Russian Engineers, in prosecution of their national 

 survey, came upon a similar anomaly in the neighborhood of their ancient 

 capital, Moscow. On tracing it to its limit, which they have done in a 

 public-spirited and most creditable manner, they concluded that there 

 is a vacuum, or a comparative vacuum, of a great many square miles in 

 extent, under the earth's surface in that country. To give some idea of the 

 reasoning which leads to so startling a conclusion, the reader may conceive 



