Tom Thomson's "Birches" 1917

The story behind "Birches" is an interesting tale and it has nothing to do with the trees. I hope you read on.

Birches
Alternate title: Northern Sunset Spring 1917
 Oil on wood panel 5 1/16 x 7 3/8 in. Smaller than
Tom's Paint Box Size of 8 7/16 x 10 9/16 in. 

The scrap of wood was about 3 inches narrower in width and height compared to Tom's typical paint box size. The oils along the short edges were smeared a bit as though the panel had been slid into a carrying case. I wonder what arrangement Tom had engineered to hold this tiny piece of wood in place while he recorded the weather observation. 

Terrain matching from Hayhurst Point looking south

It appears as though Tom did not move around too much during that last spring of 1917. A case can be made that the distant hills depicted in other sketches closely resemble the terrain of "Birches". Travel in the spring can be challenging with the ice being unsafe to walk on and with not enough open water to paddle anywhere. Tom might have simply stayed at his favourite campsite recording the awakening of nature after a long winter. If this terrain is indeed a match, then Tom was looking southerly from the crest of Hayhurst Point mere feet from his tent and favourite campsite. 

As spring progressed and milder temperatures arrived, Tom would search out the lingering patches of snow to include within his compositions. The last remnants of winter were invariably found on the north-facing flanks of hills and deeper within the shadowed forest. Such was the case with "Birches 1917". As you will discover in the following graphic though, I was more interested in the clouds. 

PowerPoint slide from Tom Thomson Was A Weatherman

The final touches to the CSI solution to this plein air sketch can be found in the least conspicuous portion of the observation - the clouds hidden behind the sparse veil of birches. Tom carefully stroked those oils between the birches. The details of colour and tone were important to him. The clouds were an important part of the observation of nature and not just window dressing for the landscape. The conclusion may be uncertain, but the search reveals some interesting meteorology and Creative Scene Investigation considerations. 

The Conveyor Belt Conceptual Model
featuring the Warm Conveyor Belt and 
the Cyclonic and Anticyclonic Companions.
The black dashed line is a typical cross-section
along the Anticyclonic Companion of the
Warm Conveyor Belt with the associated clouds.

These clouds are characteristic of a warm conveyor belt - the prima donna flow of the Conveyor Belt Conceptual Model. The line in the sky dividing the stratiform cloud from the clear blue heaven was certainly a deformation zone (see "A Closer Look at Lines in the Sky"). The orientation of a deformation zone approaching from the south is typically curved from the northwest through to the southeast with the col being in the middle of the divergent flow. The accompanying graphic of the Conveyor Belt Conceptual Model illustrates this orientation. The anticyclonic companion of the warm conveyor belt is typically the first to arrive. See the dashed, black line of the cross-section. It is characterized by stable, stratiform clouds - cirrostratus followed by altostratus. The stability of this portion of the warm conveyor belt encourages gravity waves to develop within these clouds.  Cirrus and cirrostratus clouds on the leading edge of the warm conveyor belt can be thin and diffuse. The particles comprising the altostratus cloud are more numerous making that cloud more opaque. 

The clouds were uniformly bright and warm in colour. How does one explain those qualities? The cloud did not show any change in shade toward its outer edges. The warm shades of light are achieved when Rayleigh scattering removes the cool shades of blue from the direct sun beam passing through a long expanse of atmosphere. The light illuminating the clouds is not as vivid as those of either sunrise or sunset. The timing of this plein air session thus had two options: either mid-morning or mid-afternoon. 

The concept of front and back lighting of clouds will assist us in discovering which option is most likely. (also see "Where is the sun?")The following graphic summarizes those considerations using cumulus clouds. 

A front-lit cloud is brightest in the massive central region and slightly darker on the edges. A back-lit cloud is darkest in the middle and outlined by significantly whiter edges. Those attributes are determined by Mie scattering from the relatively large cloud particles and the optical depth of the cloud mass. Back-lit, very thin clouds can be uniformly bright as they are optically thin and the sparse cloud particles preferentially forward scatter light to the observer - Mie scattering.

The mid-morning solution requires the cloud to be front-lit as illustrated in the following graphic. The sun in the eastern sky would have a clear path to illuminate the leading edge of the deformation zone clouds. The cirrus, cirrostratus or altostratus would be fully front-lit and bright with an orange tint just as Tom painted. Varying thicknesses of front-lit clouds all appear the same.

Morning illumination of the scene with front-lit, optically thick, opaque clouds

The mid-afternoon solution requires the cloud to be back-lit as illustrated below. The sun in the western sky could be potentially blocked by the thick cloud of the warm conveyor belt. The cloud behind the deformation zone would have to be thinner and more diffuse cirrus or cirrostratus so that Mie scattering did not appreciably dim the cloud and the relatively few cloud particles could still forward scatter enough light to the artist. Any variations in the optical thickness of those clouds would show up with thicker clouds being darker in the centres. These clouds all look quite uniform.  Hmm.

Afternoon illumination of the scene with back-lit, diffuse cirrus or cirrostratus

Unfortunately, there were no shadows to further aid in the diagnosis of this painting. The sun angles of both options would require the shadows to stretch laterally to Tom's view so they would not be clearly visible across the snow surface anyway. 

Sometimes it is the absence of something which is the important clue. There are no low clouds! Tom would have included any low cloud in his weather observation had it been present. 

There was not enough wind to generate turbulent stratocumulus. It was possible if not probable that the wind of the cold conveyor belt was calm or even light easterly in advance of the approaching weather system. 

Further, the lack of low cumulus clouds supports the mid-morning timing and insufficient daytime heating to generate those ground-based convective bubbles. The significant cold and reflective snow cover also impedes the efficiency of solar radiation to generate winter cumulus clouds. The deformation zone shadow as described in earlier posts (see "Tom Thomson's Spring in Algonquin Park, 1917") would not have been a factor with the sun on Tom's left shoulder. 

The lack of low clouds also makes the afternoon timing of this painting less probable given that several hours of sunshine, heating and wind would have been available to induce some kind of cloud to develop. 

Both solutions are viable from a scientific point of view but in spite of  "Northern Sunset Spring 1917" being an alternative title, I feel that a mid-morning painting session was much more likely. As mentioned in previous blogs, Lawren Harris and J.E.H. MacDonald faced a formidable challenge when they met at the Studio Building in the spring of 1918. They aimed to organize, name and authenticate the tall stack of panels. I am simply trying to add some science and other possibilities to the discussion in a positive manner.  

Birches Spring 1917 as it might have appeared in Thomson's Paint Box.
It was painted on a small scrap about 3 inches smaller in both width and
height as compared to Tom's typical paint box panels. 
I wonder what the story was behind that piece of wood? 
                                                                                                            

Inscription verso: 

• u.r., loaned by / Mr. J.T. Thomson...Brownsburg, Quebec, 1973; 
• (1970) in ink on brown paper backing, Property of / Mr. & Mrs. Geo.T. Thomson Dec. 1917 One of the two sketches sent / to me by Grandfather, / among the sketches left by / Tom Thomson at his / death in 1917; 
• G. M. Thomson; in graphite, Northern Sunset by Tom T.; 
• u.c., label, G.M. Thomson/ 38 Wellington St. / Brantford, Ont. McMichael Canadian Art Collection, Kleinburg (1979.15) (1979.15). 

Provenance:

• Estate of the artist George T. Thomson, New Haven, Connecticut and Owen Sound, 1917 
• George M. Thomson, Brantford, by descent 
• James T. Thomson, Beaconsfield, Quebec, by descent 
• McMichael Canadian Art Collection, Kleinburg (1979.15). Purchased 1979

Note that this particular inscription correctly identifies George McLaren Thomson as the son of Tom's oldest brother George as opposed to that found on the back of  "Spring in Algonquin Park, 1917"

Time and place are important clues to deciphering the story behind any creation. The hints can be subtle, sometimes based on what one cannot see. This solution may not be certain, but I feel confident in the Creative Scene Investigation approach. Tom was a morning person and probably made this weather observation on a chilly morning in late winter 1917 from the top of Hayhurst Point. There was a weather disturbance on the southern horizon. Tom saw that storm coming and recorded that weather forecast in oils on a small scrap of wood. 

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.