For those who are addicted to mobile devices（终端）, drawing provides some much needed time out. Nowadays, there is a global pencil shortage thanks to a sharp rise in the number of adults purchasing coloring books. Manufactures are reportedly struggling to deal with the heightened popularity of quality crayons（蜡笔）.

British company Faber-Castell, the world’s largest pencil supplier, witnessed “double-digit（两位数）growth” in the sale of pencils. Workers in their German factory have been asked to do extra shifts in an effort to keep up with consumer demand.

“The production of our artists’ pencils has increased strongly compared to the previous year,” Sandra Suppa from Faber-Castell tells The Independent. “People are now not satisfied with ‘just’ 36 colors and we are noticing a trend（趋势）in people preferring, bigger sets of 72 or even 120 colors for colouring. We are also noticing that people are investing in our highest quality artists’ pencils.”

Regarded as the final cure for stress and anxiety, coloring in is a way to take a break from our fast-paced digital culture. It’s not just British who are rushing to buy crayons as the trend is a global one. Staedtler, the Nuremberg-based German pencil maker, is having trouble keeping supply levels up.”We have plans for expanding our resources. Right now we’re working at our limit,” a spokesperson tells Spiegel Online. Brazil has also suffered from pencil shortages, according to NEW York Post.

Coloring books for adults are now a feature in bookshops across the world. British seller, Waterstones reported a 300 percent rise in sales of the therapeutic（有助于放松精神的）books in the past year.

Using a headset at home to deliver a low electrical current to the brain can relieve symptoms of depression. The approach, called transcranial direct current stimulation (tDCS), is effective when used several times a week for half an hour at a time.

Previous trials have shown that the treatment works under medical supervision in a clinic or lab. Now, a randomized trial has demonstrated that a tDCS headset can also reduce depression symptoms when worn at home. Depression is usually treated with talking therapies (治疗) or by taking antidepressant medicines, but these don’t help everyone.

Several forms of electrical brain stimulation may have the potential to treat depression. With tDCS, sponge electrodes (海绵电极) are placed on the left and right sides of the forehead, causing a mild current to flow from the left to the right. This makes brain cells on the left side more likely to fire, with some studies suggesting that activity in this region, known as the left is low in people with depression.

Repeated sessions of stimulation may lead to longer-term changes in the brain cells, increasing their activity levels, says team member Cynthia Fu at the University of East London. Affecting activity in this region probably changes activity in multiple areas, she says.

To see if people can benefit from using such a device at home, Fu and her colleagues tested a tDCS headset made by Swedish firm Flow Neuroscience. The team randomly assigned 174 people with moderate or severe depression to receive either a full session of stimulation from the Flow headset or stimulation from the same device that lasted just a few seconds, so people felt their skin tingling (刺痛), at the start and end of each session.

While the depression symptoms of both groups improved on a 52-point scale, those who got the real treatment showed the most benefit. Those who got the real stimulation were more likely to report skin redness and anger, however, and two people experienced burns from using sponges that had dried out.

The results may get such headsets taken more seriously by doctors, says Nick Davis at Manchester Metropolitan University, UK. “This feels really positive.” he says.

The industrial revolution was the biggest transformation in economic history. For centuries scholars have sought to understand why this process occurred in Britain around 1750. But opinions vary and some explanations are hard to prove. Researchers are now testing theories by studying why similar parts of Britain industrialized at different rates. New papers have provided evidence for a few key factors: slave-owners’ wealth, businesspersons who stood to benefit from investing, and shortages of lower-skilled workers.

Industrialization requires investment. To measure the impact of available wealth, Hans-Joachim Voth analyzed geographic variation in ownership of plantations (种植园). The wealth that Britons gained from slaves in South America flowed mainly to a few cities, such as Liverpool. By the 1830s these regions had large numbers of cotton mills and shares of workers employed in manufacturing. Other factors could have made these areas both gather wealth from slavery and industrialize quickly. But the paper tries to study slavery’s impact using slave ships’ voyages. Long journeys, caused mainly by bad weather, reduced the share of the survival of slaves and thus traders’ profits. And among similar areas, shorter trips in the 1830s meant faster industrialization.

Investors still needed to be financially driven to buy machines. In early modern Britain, most tenant farmers paid fixed rents, stopping both workers who moved elsewhere and landlords from profiting from investment. However, in 1536－40 Henry VIII ended the monasteries (修道院) and sold their land. The buyers could farm or rent it on market terms. A study by Leander shows that areas once owned by monasteries were the pioneers of industrialization. By the 1830s they had unusually large numbers of workers in trades and crafts, agricultural- machine patents(专利), textile workshops and grain separators. Those market-based farms created a commercial class and became a driving force for technological advances.

Another factor that has gained support is labour shortages. Mr. Voth studied Britain’s wars with France in 1793－1815, when there was a workforce shortage. They found that adoption of devices replacing manual labour was greatest in areas where the most men joined the army.

The strength of evidence for each of these causes implies that industrialization probably required a complex mix of conditions. Many important factors are hard to test statistically. But measuring even a few is a promising advance.