Historical information

Archival Images

These photographs came from the Wellesley College Archival Image collection on SharedShelf commons. 

A view from the waterfall in 1925. 

Construction workers adding the concrete lining to the Silver Thread in 1925. 

Silver Thread lining being constructed in 1925. 

The Alternate Plan for the Alexandra Botanic Garden in 1922. 

The Tentative Plan for Alexandra Botanic Garden in 1922. 

Historical Context

Tricia Diggins, one of the Greenhouse employees, wrote to us about her pond-related knowledge today. Her knowledge comes from her work at the Greenhouse and Botanic Gardens, as well as from her boss Del Nickerson, who has worked at the College since 1965. 

The information below are direct quotes from Tricia's email. 

Dawn Redwood Tree Area

• The liner cracked completely near the dawn redwood tree probably in the 1980's and the water didn't run past the broken area (although there are some inconsistencies about what happened and what the repair was) 
• This area of the brook is a chronic problem because the dawn redwood's roots have totally invaded the brook and need to be chopped out every year. Tree roots form mats in other areas of the brook too. The speculation is that all these breaches of the concrete cause a loss of water along the extent of the brook but I don't think the tree roots have caused much loss of water but ultimately they may crack the bed.
•  There has been a loss of rocks that were embedded in the stream for a natural effect, they just loosen over time. Sometimes the rock is lost in a key area that can change the way the water flows but sometimes it really makes little difference if the rock comes out.

Effects of Concrete

• Type of concrete is unknown
• Nick Rodenhouse told us that years ago some of his students studied the concrete pool/vernal pool in the arboretum and he said the concrete liner raised the pH in the pond making it a death trap for the amphibians breeding there. 
• I don't know if the concrete in the brook has raised the pH but perhaps in conjunction with the KOH used to raise the pH of the drinking water there is an effect. Do you have pH data for the silver thread? The two biggest pools in the silver thread, bridge pond and mirror pond, are both concrete lined so maybe the effects of the concrete would be more pronounced here since the water doesn't move through as fast but it may be countered by tannic acid from leaf litter because, although the brook is cleaned a couple of times a year, I've never cleaned the leaves from the two ponds.