268 Prof. De Morgan's Suggestion relative to Barrett's 



higher temperature than the surrounding air, and that this 

 lieated and rarefied air, together with the water globules, con- 

 stitutes a bodj' of equal or less density than an equal mass of 

 the surrounding air. But if we take into consideration the 

 slight expansion of gaseous bodies for every degree of the 

 thermometer, and compare the very great difference in den- 

 sity between air and water, and therefore the mass of heat 

 required to keep only a small quantity of water in suspension 

 for such a considerable time; further, if we ask, why by 

 such an elevation of the temperature of the air in contact with 

 the water globules the capacity for saturation of this air may 

 not increase with the temperature, and the minute water glo- 

 bules be not converted into water gas again ; — all these cir- 

 cumstances present difficulties almost insurmountable in 

 adopting this theory. 



M. Saigey finally declares, that the equilibrium of the clouds 

 is only apparent; that the minute globules of water in the cloud 

 were indeed constantly falling, but immediately as they left 

 the cloud were again converted into water-gas by touching 

 the surrounding non-saturated air, which rising and cooled 

 down again, restored again its water to the cloud, so that all 

 these clouds were constantly losing water on one and re- 

 ceiving it on the other side. This explanation can only be 

 correct under certain circumstances, that is when the cloud 

 is near its decomposition. The sharp definite outlines and the 

 circumscribed forms of the clouds swimming in a clear and dry 

 sky, prove that they are not further connected with the cause 

 of their origin; besides, their swimming so long in the air un- 

 altered in form during very widely different degrees of tem- 

 perature, and their movement often in different directions 

 coming in contact with each other, and separating again un- 

 altered in shape, all proves too well their substantiality, or 

 rather their individuality. 



XLV. A Suggestion relative to Barrett's Method of comjmting 

 the Values of Life Contingencies. By A. De Morgan, i^g. 

 Professor of Mathematics in University College*. 



nPHE method of calculating the value of life contingencies, 

 -*■ which is called after Mr. Barrett, its inventor, has been 

 rapidly coming into use of late years, and is well known by 

 those who are used to it, to save much the greater part of the 

 time and labour required by the common methods. The use 

 of this method will be much extended by the copious tables 

 published by Mr. Jones in the " Library of Useful Know- 

 * Coniinunicated by the Author, 



