72 AMERICAN ASSOCIATION EOB THE ADTANCEMENT OE SCIENCE. 



a single year's mortality." The formula is, that, for the age x, the rate of mor- 

 tality or the ratio of the dead to the living for that age is expressed by 



a b 

 ■where, a, b, c, are constants which differ for different tables. From this the Pro- 

 fessor drew the folloAving conclusions ; 



1. The rate of mortality invariably increases from youth to old age. 



2. This rate is continually accelerated even in a higher ratio than in geometri- 

 cal progression. 



3. In early manhood, the rate does not differ much from a slow arithmetical 

 progression. 



4. There are no crises or climacterics at which the chaDces for life are stationary 

 or improving. 



5. There are no periods of slow and rapid increase succeeding each other ; but 

 one steady, invariable progress. 



6. The law, though not the rate of mortality, is the same for city and country, 

 for healthy and unhealthy places, for every age and country and locality; and 

 this law is that the differences of the logarithms of the rates of mortality are in 

 geometrical progression. 



OZONE OBSERVATION. 



Prof. Rogers gave an account of some observations made by him on the existence 

 of ozone in the atmosphere. In the first instance these were made at BostoD, and 

 he here found winds blowing from the sea heavily ozonised, while those from the 

 land were less so ; on removing, however, fifty miles inland, he found the indica- 

 tions of ozone apparently independent of the quarter from which the wind was 

 blowing, and depending more on its velocity ; in a calm there being but slight 

 ozouic effect, the increase being marked with the violence of the wind. This wes 

 to have been expected from the imperfect character of the mode of observation, 

 since the effect produced on the test paper would depend on the quantity of ozone 

 brought in contact with it, and this of course depended on the quantity of air that 

 passed over it in a given time. To remedy this defect, he had arranged an 

 apparatus by which the number of cubic feet of air passing over the test paper 

 could be measured. 



Dr. Webster, of Norfolk, added an important observation, "Last year, while 

 the yellow fever was at Norfolk and Portsmouth, I kept an ozonometer constantly 

 exposed to the air, and never delected ozone. This year I have used the ozonometer 

 in the same place, and at the same period of time, and I find ozone in abundance." 



THERMIC EFFECT OF THE SUN'S EATS. 



In a paper, by Mrs. Eunice Foote, some interesting results of experiments on 

 this subject were given. The experiments were made by exposing freely to the 

 Sun's rays a thermometer, with blackened bulb, enclosed in a glass receiver, 

 which contained the various gases experimented on. The effect was found to be 

 greatest of all in Carbonic Acid gas : for example, when in air the thermometer 

 stood at 106°, in Hydrogen it stood at 104° ; in Oxygen, at 108°, and in Carbonic 

 A.cid at 125°. It was also found that the thermic effect was increased in air by 

 an increase of its density and also by an increase of the moisture in it. 



(To be continued.) 



