Thomas Edison Accepts Congratulations on the “Thirty-fifth anniversary of the incandescent lamp”

In the period from 1878 to 1880, Thomas Edison and his associates sought to develop a viable and efficient incandescent lamp. Incandescent lamps would make artificial light, and fulfill a dream that mankind had had of a light source people could control to brighten up the night. The light would be created by using electricity to heat a thin strip of material (called a filament) until it gets hot enough to glow. Other inventors had tried to perfect incandescent lamps but had failed. The Edison lab worked on at least 3,000 different filaments in their search for a practical solution. The lamp Edison created would consist of a filament housed in a glass vacuum bulb. He had his own glass blowing shed where the fragile bulbs were carefully crafted for his experiments. Edison was also trying to come up with a high resistance system that could eventually mean small electric lights suitable for home use.

On October 14, 1878, Edison filed his first patent application for “Improvement In Electric Lights”. However, he continued to test several types of material for metal filaments to improve upon his original design. He finally decided to try a carbonized cotton thread filament. On October 21, 1879, when voltage was applied to the completed carbon-filament bulb, it began to radiate a soft orange glow. And fifteen hours later the filament was still lighting; this then was the first practical electric light. On November 4, 1879, Edison filed another U.S. patent for an electric lamp using “a carbon filament or strip coiled and connected … to platina contact wires.” Edison and his team finally discovered that a carbonized bamboo filament could last over 1200 hours. This discovery marked the beginning of commerically manufactured light bulbs, and in 1880 Thomas Edison’s company, Edison Electric Light Company, began marketing its new product.

Robert F. Pack had a long history of interest in electric lights. In 1912 he became president of the Canadian Electrical Association, then went on to Minnesota where he became General Manager of the Minneapolis General Electric Company. In 1922 his service would be rewarded when he became vice president of the National Electric Light Association in the United States. He sent Edison a letter congratulating him on the 35th anniversary of his invention of the light bulb.

This is Edison’s response. Typed letter signed, on his laboratory letterhead, Orange, N.J., November 7, 1914, to Pack. “On my return from an automobile trip to Detroit I find awaiting me your telegram of congratulations on the Thirty-fifth anniversary of the incandescent lamp. Allow me to express my appreciation of your courteous remembrance of the occasion, and to thank you for all your good wishes in my behalf.”

The is the first letter we have had of Edison mentioning his invention of the light bulb, and a search of public sale records going back 40 years fails to turn even one. We obtained it from the Pack descendants, and it has never before been offered for sale.