Welcome back Middlemay. As always thank you for the insightful comments and discussions last week. As always a summary, some references and some questions in the comments. Alternatively ask your own questions or just offer you own thoughts and observations. To Middlemarch....

SUMMARY

We get a perspective shift from Dorothea to Mr. Casaubon and his (rather unromantic) reasons for marrying, and the expectation that his happiness is the responsibility of his wife. Will Ladislow has written a letter to Mr. Casaubon requesting to visit in which is included a letter addressed to Dorothea. Mr. Casaubon is not happy about either events and ends up having a disagreement with Dorothea. Dorothea speaks up for herself and they work in silence for a while. Suddenly Mr. Casaubon is unwell and gasping for breath on the library steps. Dorothea gets him to the sofa when Sir James arrives in time to send the butler for Mr. Lydgate. Sir James reflects on how someone should have stopped the marriage between Dorothea and Casaubon (specifically Mr. Brooke).

Mr. Casaubon looks like he is on the mend but Mr. Lydgate is wary and advises Mr. Casaubon to relax. Dorothea knows this is easier said than done, but Mr. Lydgate states he could have a second attack at any time. Dorothea asks Mr. Brooke to write to Will and tell him about Mr. Casaubon's health. Mr. Brooke writes 3 pages and ends up inviting Will to stay with him at Tipton Grange.

REFERENCES

• Parergon is a piece of work that is supplementary to or a by-product of a larger work. This was how Mr. Casaubin referred to his work.
• The leading minds of Brasenose - Brasenose (previously Brazen Nose College, named for its 13th century doorknocker) is one if the constituent colleges of Oxford University. 
• Mr. Casaubon's dedication to Carp read "viros nullo ævo perituros" and losely means no men ages doomed" (Carp, Pike and Tench are all fellow mythologers) why exactly this was so embarassing for Mr. Casaubon, however, is unclear.
• Mr. Lydgate uses a stethoscope on Mr. Casaubon and that was not yet standard. Interestingly (from Wikipedia) "The stethoscope was invented in France in 1816 by René Laennec at the Necker-Enfants Malades Hospital in Paris. It consisted of a wooden tube and was monaural. Laennec invented the stethoscope because he was not comfortable placing his ear directly onto a woman's chest to listen to her heart. He observed that a rolled piece of paper, placed between the patient's chest and his ear, could amplify heart sounds without requiring physical contact. Laennec's device was similar to the common ear trumpet, a historical form of hearing aid; indeed, his invention was almost indistinguishable in structure and function from the trumpet, which was commonly called a "microphone". Laennec called his device the "stethoscope" (stetho-   -scope, "chest scope")...."
• tow-picking - pulling something out hauling something. Mr. Casaubon thoughts on Mr. Brooke's suggestion he takes up a hobby.
• Conchology - a hobby suggestion from Mr. Brooke and it is exactly what you would guess it to be. The study of mollusc shells.