TRANSACTIONS OK SECTION B. 693 



suggestions I have made should prove to be of practical value, and should lead 

 to the production of more original research by our students, I shall feel that a 

 useful purpose has been served by bringing this matter before this Section. In 

 concluding I wish to thank Professor H. B. Dixon, Professor F. S. Kipping, and 

 others, for many valuable suggestions, and my thanks are especially due to Dr. 

 Bevan Lean for much information which he gave me in connection with that 

 part of this Address which deals with the teaching of chemistry in schools. 



The following Reports and Papers were read : — 



1. Reijort on the Teaching of Science in Elementary Schools. 

 See Reports, p. 187. 



2. On some Problems connected ivith Atmospheric Carbonic Anhydride, and 

 on a Neio and Accurate Method for determiriing its Amount, suitable 

 for Scientific Expeditions. By Professor Letts, D.Sc, Ph.D., <tc., 

 and a. F. Blake, F.I.C, F.C.S., Queerus College, Belfast. 



Attention is drawn to the variations in the amount of atmospheric carbonic 

 anhydride which correspond with at least 10 per cent, of the total amount, the 

 causes of which are still to a large extent obscure. In the author's opinion the 

 subject is an important one, and is worthy of a systematic investigation bv a 

 number of skilled observers working in different localities and employing tLe same 

 method of determination which shall have been proved to give results which do 

 not vary from the true amount by more than three or four parts per million of 

 air. Among the problems relating to atmospheric carbonic anhydride which 

 the authors think are specially deserving of attention are the following : — 



1. Is Schloesinfs Theory Correct ? — Do the oceans really act as regulators of the 

 amount of atmospheric carbonic anhydride by the production or dissociation of 

 earthy bicarbonates according as the amount rises above the normal or falls below 

 it ? As consequences of this theory latitude should influence the quantity of 

 atmospheric carbonic anhydride, which ought to be lower in polar than in tropical 

 localities, and the great ocean currents should also have an effect as they pass from 

 warmer to colder regions, or the opposite. 



2. The Infuetice of Day and Night, at Sea. — To account for the increased 

 quantity of atmospheric carbonic anhydride over land surfaces at night, which 

 most of the observers have found, two theories have been advanced : («) cessation 

 of plant activity in decomposing the gas owing to the absence of light, and {b) the 

 streaming out of crouud air from the soil owing to the lowering of temperature. 



At sea no such influences can be exerted, but an absorption of atmospheric 

 carbonic anhydride may occur at the surface of the water owing to lowering of 

 temperature, thus reversing the land efiect. 



'6. The Effects of Atmospheric Precipitates, and especially of Snoufall, zvhich 

 appears to increase the amount of Atmospheric Carbonic Anhydride. — No reason- 

 able theory has been advanced to account for this curious phenomenon, and it 

 would be interesting to ascertain whether it occurs at sea as well as on land ; and 

 the same remark would apply to fog and rain, both of which appear to afiect the 

 amount also. 



Other supposed causes of variation are worth studying, such as the effects of the 

 seasons, direction and force of the winds, the prevailing type of weather, &c. But 

 those which the authors think most interesting are such as a scientific mission 

 would be under peculiarly favourable conditions for observing, and especially the 

 proposed Antarctic expeditions. 



In a memoir of the authors recently published in the ' Proceedings of the Royal 

 Dublin Society ' (vol. ix. N.S., Part \i. No. 15) a modification of Pettenkofer'a 



