The Zoologist — November, 1873. 3757 



August, 1828, is still alive and well. But Sir John knew nothing of 

 employing plants to evolve oxygen, and therefore to preserve a balance of 

 life with unchanged water, though Dr. Joseph Priestley (1733 — 1804), the 

 discoverer of oxygen gas, and the first observer of the fact that that gas is 

 emitted by plants under the influence of light, and therefore the earliest 

 enunciator of the main principle on which the maintenance of aquariums 

 depends, had published this discovery and observations. Ingenhousz also 

 had shown that plants evolved this gas. Therefore if Dalyell knew this, he 

 did not apply the principle." — ' Handbook,' p. 9. 



However, T have a widely different object in introducing this 

 notice of Sir John's aquariums and their success. Mr. Lloyd, who 

 never leaves a stone unturned if there be a chance of finding a 

 particle of information beneath it, obtained access to Sir John's 

 quartos,* with a view of ascertaining his practice, his experience, 

 and his views, at a period when this now engrossing subject was 

 almost totally ignored ; but in doing so he found explanations that 

 required explaining. Miss Dalyell, a sister of ihe Baronet, was then 

 still living in Edinburgh, and, although at the advanced age of 

 nearly a hundred years, was in full possession of her faculties and 

 her memory : he therefore conceived the idea of framing a series of 

 questions on those points which appeared obscure, and of respect- 

 fully soliciting information. It was indeed a bold step, but a suc- 

 cessful one. To these questions Miss Dalyell most obligingly sent 

 the following categorical replies, which cannot fail to be read with 

 the deepest interest. My sincere thanks are due to Mr. Lloyd for 

 having, unsolicited and unreservedly, placed these letters in ray 

 hands for the express purpose of illustrating this notice of his 

 'Handbook.' Miss Dalyell's replies evince a wonderful retention 

 of faculties to extreme old age, but also prove what an observant 

 and intelligent interest she must have taken, during very many 

 years, in her brother's scientific pursuits. 



Letter I. 

 Miss E. Dalyell to Mr. W. A. Lloyd. 



8, St. Colme Street, 2 January, i860. 

 Sir, — In answer to your enquiries regarding the way Sir John Graham 

 Dalyell kept his marine animals, I will certainly give you all the information 



* ' Eare and EemarkaUe Animals of Scotland.' By Sir John Graham Dalyell, Bart. 

 2 vols. 4to, 1847—8. And 'The Powers of the Creator displayed in the Creation.' 

 Same author. 3 vols. 4to, 1851 — 8. 



SECOND SEIUES — VOL. VIII. 3 H 



