Tom Thomson's Blue Clouds, Wooded Hills, and Marshes Summer 1915

This is another one of those panels from the stack of Thomson's paintings retrieved from the Shack just south of the Studio Building at 25 Severn Street in downtown Toronto at the edge of the Rosedale Ravine. In the spring of 1918 Lawren Harris and J.E.H. MacDonald had a mountainous and virtually impossible task to sort through Tom's efforts of the previous three years. The title of this panel is certainly unique as it describes everything they saw in those brush strokes. But there is much more to the story. Please let me explain...

Blue Clouds, Wooded Hills, and Marshes Summer 1915
Oil on wood -pulp board 8 1/2 x 10 9/16 in. (21.6 x 26.8 cm)
Tom's Paint Box Size - 1915.67

Typically Creative Scene Investigation (CSI) starts with establishing the location of the plein air experience. That step is important because it establishes the viewing direction of the artist. In this case, those hills might be almost anywhere. In previous posts, discovering the exact location and time were more challenging than understanding the science and frankly, I find it exhausting. In this example, the science will uniquely establish the direction of view and the time even without knowing the location. 

The next step in CSI is to study the painting and identify everything one can see. For example, the large size of the convective elements at the horizon identifies those clouds as cumulus. If you were standing under those clouds, you would need the entire hand of your extended arm to cover up the convective elements. If those convective clouds were altocumulus (between 6500 and 20,000 feet above the surface), your thumb would block out those cloud pieces. Even higher overhead convective elements like cirrocumulus above 20,000 feet can be obscured by just the tip of the baby finger on your outstretched hand.  

The next features of particular interest were the very long and bold brush strokes radiating from a point below and to the right of the picture plane - the sun 93 million miles away. Tom was using colour and singular strokes to capture crepuscular rays radiating from the sun. The nature of crepuscular rays is described in the following graphic. They can occur at both sunrise and sunset and just require particles in the air to forward scatter light to the observer. Clouds sometimes block the direct beam from the sun thus creating a "crepuscular shadow".  The contrast between crepuscular rays of light and shadows can really make the phenomenon vivid, especially at low sun angles. 

In this case, cirrostratus ice crystals were forward scattering the light (Mie scattering) of the crepuscular rays. There were no optically thick, high-level clouds to create obvious crepuscular shadows. Notice there was also no blue sky in sight and the sky was overcast in cirrostratus. The upper levels to the left of the painting showed where the rays of the sun were not able to reach and the twilight sky of night was advancing. This is evident in both Tom's painting and the sunset photo.

The important clue that surprised me was that the left faces of the cumulus clouds were brighter than the right. How could this be if the sun was behind the horizon? There had to be a second source of light! 

The only answer to this rhetorical question is that a nearly full moon was illuminating the cumulus cloud faces. A full moon can only rise above the eastern horizon in the early evening exactly opposite to the sun is sinking in the west. The illumination of the cumulus clouds unequivocally proves that Tom was looking west at sunset and that a nearly full moon had risen in the east over his left shoulder. 

There is more to discover though. The crepuscular rays originate from well below the western horizon proving that the timing of Tom’s plein air experience was certainly after sunset. The light of the moon on the southeastern flanks of the cumulus clouds was rather white. The colour reveals that the path of the moonlight to the face of the cumulus clouds was not through a long atmospheric path. The moon had to be relatively high in the twilight sky. This fact further reveals that although nearly full, the moon was in its waning gibbous phase. A waning gibbous moon is a couple of days past full and rises before the sun has set. A waning moon is higher in the twilight sky before the sun is below the western horizon. The following graphic details the path of the light from the sun to the cumulus clouds.

Note that there is no scattering of the sunlight on its path to the moon through the vacuum of space. All of the colours of the rainbow that comprise white light would illuminate the face of the moon. That white light must pass through some of the atmosphere of the earth to reach the cumulus clouds. In this case, that path was not long enough to tint the light to the longer wavelengths of red. Rayleigh scattering of the shorter blue wavelengths out of the beam from the moon is required to shift the light to reddish shades and that was clearly not happening. 

Recall as well that after sunset, the foreground must be back-lit and void of colour.  In "Blue Clouds, Wooded Hills, and Marshes Summer" that is definitely not the case. The marsh has colours and lots of interesting shapes that Tom could see and paint in the moonlight! The waning gibbous moon sheds light on the scene as well as the cumulus. 

In addition, cumulus clouds as vigorous as Tom painted typically require a daytime of heating. The sun heats the ground which in turn warms the adjacent air. The warm air rises convectively like hot air balloons. The clouds also appear to be well aligned suggesting that some organized triggering feature was responsible for their organization. An approaching cold front would nicely explain everything Tom painted. 

Note as well that the bases of the line of cumulus clouds were very low and hidden by the distant hills. The lifted condensation level of the air mass had to be very low. This reveals that Tom was located within a warm and moist air mass which is an essential component of every mid-latitude weather system. 

These particular towers of cumulus were also tipped toward the south (left). The winds at the surface are reduced through friction while the winds aloft are relatively unhindered. The resulting wind shear encourages the towers to lean forward as they approach. 

The cirrostratus would be associated with the warm conveyor belt of the system. The cirrostratus is included in the following graphic as a white veil on the warm side of the jet stream - to the right of the flow as you look in the direction of the wind. 

The graphic above includes the likely location of Tom just ahead of the approaching cold front. The cumulus towers triggered by and organized along the cold front are the three convective clouds west of Tom. A thin veil of cirrostratus is included above the entire weather system in the graphic. 

The "cogs" referred to in the above graphic convert the wind of the jet stream into rotational energy that shapes the weather system. The red cogs rotate cyclonically and can be visualized by using your Coriolis Hand (right hand in the northern hemisphere) and pointing your thumb upward at the red "X". The fingers of your Coriolis Hand must curl in the same direction as the rotation of the atmosphere. The blue cogs rotate anticyclonically and are visualized by pointing your thumb downward at the blue "N".. These circulations are linked in three dimensions and evolve with time and the weather. See "The Theory of Unified Swirls" as well as others in that series about meteorology which are linked from that blog. Differential advection of the rotational energy by the wind causes the air to either rise or sink - and that is the very short explanation of the weather!

In any event, cooler, drier weather with northwesterly breezes was on the way for wherever Tom happened to be while painting that sunset sky. 

Blue Clouds, Wooded Hills, and Marshes Summer 1915

Tom chose not to record the waning gibbous moon rising in the east but instead was drawn to the front-lit cumulus and crepuscular rays in the sunset sky to the west. Perhaps he did turn to also observe the waning gibbous moon but not in this particular panel.

I find it interesting that blue clouds, wooded hills, and marshes are what Harris and MacDonald saw in this painting. I suppose there is a tint of blue to the sunlight reflected off the face of the moon and illuminating the southeastern flanks of the cumulus. Perhaps the blue they were referring to was the twilight colour in the cirrostratus overhead. 

Tom was possibly inspired by the double sources of illumination although all of that light must originate from the sun as explained above. We will never know for sure. I just wish that he had made a few notes about what caught his eye and where he happened to be. It would make for interesting reading more than a century later. 

There is even more to this story! This painting reminded my Thomson friend of the terrain around Whitson Lake. See "Tom Thomson's Spring Sunset, Algonquin Park Spring 1916" for a description of two paintings he did from that location. The orographic features identified in "Spring Sunset, Algonquin Park, Spring 1916" looking westward bears more than a passing resemblance to those in "Blue Clouds, Wooded Hills, and Marshes Summer 1915". The marsh is the obvious match but the hills and ridges may also be identified. The vantage for this painting would be from just a bit to the north at the red star in the following graphic. The view would be roughly between the red arrows. The unnumbered hill was just not quite high enough to reach another orographic contour. 

My Thomson friend who is very familiar with the Whitson Lake area noted: 

"Tom wouldn't have been right at the shore, as it slopes down to the water fairly steeply there, but up at the same level as the other presumed Whitson Lake sketches his view could well have been as you suggest.  One has to assume the forest had been pretty well clearcut there (which it no doubt had been).  There is a wet area back in there, and clearly at one time there was a beaver pond, but it is now just a marshy seep with a few dead tree trunks sticking up.  I wonder if it was really summer or perhaps very early fall, with some of the wetland vegetation having already changed colour to some extent.  Tom and Ed Godin would have passed that  location on their 1916 canoe trip on the Petawawa.  (The previous Whitson Lake sketches, and most likely also Bateaux, were obviously summer.)"

The preceding detail demonstrates how important it is to have boots on the ground that have travelled the same paths as Tom Thomson. The special and personal knowledge does not come easily without years of effort and research. If this painting's location was indeed Whitson Lake, then the 1915 dating is also in doubt. Similar inaccuracies have already been noted in Thomson's catalogue raisonné. The task of creating an accurate catalogue raisonné without additional information provided by the artist would be impossible. 

The more you look, the more you see and the more you find... It is vital to maintain a natural curiosity when investigating Tom's art and most importantly, an open mind. 

Inscription recto: 

• l.r., estate stamp 

The estate stamp was applied to the lower-right corner by one of the following friends of Tom.

Patron Dr. James MacCallum funded the Thomson Estate Stamp which was designed by MacDonald

Dr. James Metcalfe MacCallum
 (1860–1943)

Inscription verso: 

• c. and l.r., estate stamp;
• u.l., in ink, AM; 
• l.c., in ink, 90/10; 
• c.r., label, James M. MacCallum 90/10 and in graphite, 
• l.r., 6 National Gallery of Canada, Ottawa (4652) 

Provenance: 

• Dr. J.M. MacCallum, Toronto 
• National Gallery of Canada, Ottawa (4652).
• Bequest of Dr. J.M. MacCallum, Toronto, 1944

The weather story was subtle but I do hope that you found it interesting. Thank you again Dr. MacCallum for recognizing Tom's artistic gifts and sharing them with the people of Canada. 

Warmest regards and keep your paddle in the water,

Phil Chadwick

PS: Tom Thomson Was A Weatherman - Summary As of Now contains all of the entries to date. 

PSS: Should you wish to have Creative Scene Investigation applied to one of Thomson's works that I have not yet included in this Blog, please let me know. It may already be completed but not yet posted. In any event, I will move your request to the top of the list. If you made it this far, thanks for reading!