March 27, 18M. ) 



JOUENAL OF HORTICULTURE AND COTTAGE GARDENER. 



243 



tube. ABsnming that at a given time the thermometer can be 

 so tilted by clockwork (as I will hereafter show to be the case), 

 how is this quantity of detached mercury to be measured? in 

 other words, when a person comes to his thermometer some 

 hours after the portion has been detached, how is the temper- 

 ature which was existing at the moment of separation to be 

 ascertained ? The portion of mercury detached must be mea- 

 sured, and the measurement is made in this way : Suppose the 

 mercury when the thermometer is placed in a vertical position, 

 bulb downwards, stands at 50°, it will be found on tilting the 

 thermometer and detaching the mercury for experiment to the 

 other end of the tube, that the upper surface of the detached 

 portion wiH read off at or near some of the degrees on the or- 

 dinary scale of the thermometer. On the opposite side of the 

 graduated part of the instrument a small slip of paper must 

 be fixed by glue or some similar adhesive substance along the 

 whole length of the tube. Should a thermometer, when placed 

 vertically, read at 50', care must be taken to note the height 

 on the paper where the detached portion of the mercury ap- 

 pears on tilting, and note that spot 50 ' likewise. This plan is 

 to be adopted at different temperatures throughout the scale, 

 and by such means the temperature when the thermometer is 

 tilted and reversed can be ascertained, or such a scale can be 

 engraved by the maker. The instrument is reversed at the 

 time that is desired by means of the weight of an alarum 

 clock. As the weight descends, the thermometer which is in 

 connection with it, is made to fall to a position considerably 

 below the horizontal. I purpose now to give drawings of a 



thermometer both before and after it has been set in motion by 

 the alarum clock, with the machinery also which reverses the 

 thermometer, and by such drawings I hope to convey to your 

 readers a much better idea of the thermometer apparatus than 

 I have done by the past description. 



I have only cursorily glanced at this invention ; but suffici- 

 ently, I think, to give your readers an opportunity of judging how 

 far such a thermometer apparatus may be useful to them. I 

 have no doubt but that many already possess a maximum ther- 

 mometer, such as I have described, and most, if not all, a small 

 alarum clock with weights. That is really all the machinery re- 

 quired for the apparatus in its simplest form. The working 

 of thermometers which register the maximum and minimum 

 is wcJl known to all. In the morning the observer knows 

 how low or how high the temperature has been during the 

 night. My plan will not tell him when the lowest or highest 

 temperatures occurred, as is the case when a jihotographic ap- 

 paratus is Used, but it will give him the temperature of that 

 moment when the alarum descended, and the alarum must be 

 set for the time when he wishes to know existing temperatures. 

 I think in many instances that such knowledge will be of use 

 to a gardener and others, and will give them respectively in- 

 formation how fires have been working up to that fixed time, 

 whether proper temperatures were then existing in a room, or 

 the degrees of cold or heat in the external air, and that not by 

 getting up in the middle of the night, or by being on the spot 

 by day, but by reading off by the new scale the height at which 

 the mercury stood when the weight of the alarum ran down. 



Fig. 1. 



Piece of wood, c c c. Coarse of thermometer, 

 w. Alarum weight, x. Hook to alarum. 



Fig. 2. 



H H. Hooks. M. Height of mercm-y in tube. n. A nail. o. Obstruction in tube, s s. String. i\ 

 D M. Detached mercury, t. Part of thermometer inverted, with new and old scale. 4" 



In choosing a thermometer for the purpose great care must be 

 taken to see that the mercury does by its own weight easily 

 pass the obstruction in the tube when the instrument is placed 

 in a vertical position, and also that, when the thermometer is 

 tilted, the mercury detaches itself without difficulty at the point 

 of obstruction and proceeds to the farthest end of the tube. 

 This previous caution is necessary, for unless the mercury acts 

 in the way above mentioned (although such an instrument is 

 perfect as a maximum thermometer), it will be of no use for 

 recording temperature at any one given time. I now proceed 

 to describe the temperature-recording apparatus. 



Figs. 1 and 2 represent the invention in its two different 

 stages ; the one (fir/. 1) a moment before the alarum has gone off, 

 the other {lig. 2| when the weight of the alarum has descended 

 and the thermometer is no longer in the same vertical position 

 as before. 



I will now glance more particularly at the general machinery 

 necessary to carry out such a change, and, first, I will describe 

 the mode of settingup a thermometer as it appears injig. 1. 



Against the wall of a greenhouse fix (secure from dripping of 

 water), and set going a clock which is furnished with an alarum 

 weight, w, at the bottom of which is a small hook, x. I will 

 suppose the time at the moment of starting the pendulum, and 

 binding up the alarimi to be G p.m., and that the temperature 



of the place at 12, midnight, is required to be known. Set the 

 alarum for 12, midnight. In the wall drive in or screw hooks 

 at H, H, and at s fix a maximum thermometer which plays 

 freely on a nail, n. Connect the thermometer with the alanmi 

 weight, w, by means of a string, s, s, s, fastened to the hook, x, 

 and passing round the hooks, h, h. The instrument now acts 

 as an ordinary thermometer, the mercury stands up to m, and 

 passes the obstruction at the bulb, o. As the temperature 

 varies, so will the mercury rise or fall in the tube ; but at 12, 

 midnight, the scene will be changed. The weight, w, will de- 

 scend ; the thermometer turning on n, as on a pivot, will pass 

 through c, c, c, and will present an appearance similar to that 

 observed in the second drawing. Jig. 2. Now, what has really 

 taken place ? A quantity of mercury has been detached at o, 

 and has run down to the end of the tube, marked dm (detached 

 mercury). The instrument cannot run down to a lower posi- 

 tion than that indicated in Jig. 2, owing to a small piece of 

 wood, A, which prevents the weight, w, descending farther. 

 This will be better understood if the reader look at the posi- 

 tion of A as represented in Jig. 1. Care must be taken also to see 

 that the mercury has run down to the end of the tube before 

 reading off the degrees of temperature by the new scale, Y, 

 which represents part of a thermometer inverted with the mer- 

 cury run down. Should an increase of temperature have taken 



